Usually just use cable ties to tighten the silicone water hose around the inlet and outlet without sealant, as far as I know.
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thanks again - I’ll add to this trail once it comes. Really appreciate your advice and assistance.
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here are the silicone sleeves I was going to order. What then would the sealant be required for?
Stop! They are not the right ones.
I’ve seen them on here somewhere… ill take a look.
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ok, great, thanks 
Here you go - someone has been on your journey already 
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cheers So basically twist the wires together and seal as much as possible with tubing and silicone!!
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If your tube already has a wire attached I would recommend these connectors.
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this is what I see available in the uk
I think you don’t want the connectors already connected though.
If you can’t get the plain connectors that @NedMan linked to, I’d suggest the “twist and seal with silicone tubing and sealant” option. You can leave a bit of extra wire and order some of those plain connectors to attach the next time you open the box.
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The best advice I can give:
Take a photo of how the tube currently sits (how close to mirror 1 and how highly) this will make mirror alignment easier.
If your machine doesn’t currently have a high voltage connector, get one. It’ll save you time and give you peace of mind. It’ll make future tube changes easier too.
Don’t think about it too much, I’d never done it before and managed to swap it out in 10 minutes, it’s been running great ever since. Feel free to message me if you have any questions
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can’t seem to find the right high voltage connectors on Amazon UK. Any advice on the right one? And yes @renegadeltd I am probably thinking too much about it. Probably will continue to until the tube arrives in a few days 
I got mine from eBay - grey goose I think the company is called. They are the company that are the distributors for mini grbl board
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That’s a very kind offer! May I request at-mentioning in this thread instead of messaging? That way, the next person who has the question can find the answer, too. I’d like to highlight that there really aren’t “dumb questions” here — no need for anyone to be afraid that a question is too obvious to ask.
Also no one should need to fear to ask again a question that has already been answered. It’s often the case that if you know what to search for, you don’t need to ask the question! I often respond to questions with links to answers inside Maker Forums, but that’s not a passive-aggressive “lmgtfy” response — I’m building a web of questions and answers to make the questions and answers more useful. There’s a wide gap between an answer being somewhere on the site and being able to figure out what to search for to find it, and having a few different expressions of the question makes it easier for the next person to be able to search for it. 
So while it’s good to 
search for answers, no one should be penalized for not knowing how to find them.
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Thanks all so far for all the advice. So I looked at my laser tube again. There are 3 wires coming from the machine. 2 black and a red. Assuming the red is the +ve and is connected directly to the +ve of the tube. And one of the black is the -ve, also connected directly to the tube. The other black is taped with electrical tape to the outlet water tube. So, I’m assuming I am going to need 2 high voltage connections for the +ve and -ve wires to connect to the new tube but wondering is the 2nd black an earth?Pics below.
You only need one HV connector for the red wire.
The other black tube connection is the cathode and is connected to ground so it does not have to be HV.
The third connection looks like a temperature sensor. Have not see one like that before. Where does the other end connect?
In any case you should not have to mess with it as the water tube will not be replaced, just disconnect and then re-connect.
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Many thanks @donkjr The black cathode is connected to the tube, so what you’re saying is just to connect the cathode on the new tube to the same on the machine in the normal way (twist together and seal with tape?)
Yes, as a default just re-attach it like it currently is. This is a low current connection that should be at ground (no voltage).
If it is just wound around the pin I prefer to have a slip on connection for this end since it is such low voltage and current. I took a pin from an old connector that slid on easily and soldered it to the wire and then slid the pin on the post.
Either way should work.
Do not put any force or heat on either of the posts or they may crack the tube.
The other end of the cathode wire should go to:
… your meter if you have one
or
… to the FG on your LPS if you have a digital panel.
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The one with the tape its temp sensor, i had the same on my machine.
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an electrician friend of mins just dropped by (the tube isn’t here yet) but thinks that these would be good enough to connect the wires, obviously tape over with electrical tape. The reasoning (I think) is that the 20,000+ volts aren’t generated at this junction seeing the tube is already wired. It’s just joining the lead coming form the power supply to the lead that goes to the +ve terminal on the tube. Thoughts?