I have done some research and read a couple of great threads, and learned the basics but I'm still finding it a bit daunting, I stumbled upon the AQUATEK CO2 Regulator with Integrated COOL TOUCH Solenoid, which seems to have a lot of good things said about it and not being so good at DIY I thought this would be a better option than building my own and risk wasting my cash, how ever a guy on youtube said the Solenoid once it switches on again it don't stay at the same bps and needs to be re-adjusted which I don't really want, so how could this be fixed, this is why I am now thinking of maybe building my own, depending on cost.
I personally would not recommend the mass produced, commercially available regulators, as since they are mass produced, you will inevitably run into problems with some of the units. Many people have had good experiences using these regulators, while others have not, so it is up to you to decide whether or not to purchase it.
My next problem is I am from the UK so, does a USA Regulator work on UK CO2 Cylinders, and also if I purchased a CO2 Cylinder from USA can I get that re-filled in the UK?, because I have read information saying they just swap cylinders, maybe the connections are different?
Most likely not. The British standard is likely different from the North American standard, so regulators and CO2 cylinders are not interchangeable.
My next problem lol, is that I can't find anywhere in the UK that sells CO2 Cylinders, and I found some pub/beer sites that do, but there CO2 mixes are 50/50 or 40/70 which is really confusing, not even sure what there on about.
Home brewing sites should have CO2 cylinders. You can also check out hydroponics stores and also fire extinguisher websites.
The 50/50 and 40/70 mixture that you are indicating are likely mixtures of CO2 and N2.
I've also done research on what other UK people in general do, and all I've found is that... people have purchased lovely CO2 cylinders from USA, to then get them re-filled and the people turn around and say we don't refill but we swap, so then you have to swap your brand new lovely cylinder for a old second hand one...
Each refill place is different, so you will need to ensure that the place that will do your refill does a on the spot refill, and not a cylinder swap as you have described (this is if you want to keep your CO2 cylinder).
I did find a good youtube video about a guy who uses refurbished CO2 fire extinguisher's but then he started dipping it all in water, and was mentioning about you don't want co2 leaking into your room which is worrying.
I also use a CO2 fire extinguisher. Aside from the bright red paint on the outside, there is nothing wrong with using one.
Dipping the connections in soapy water is to simply ensure there are no leaks. Small CO2 leaks are more annoying (and less so a danger to your health), as they can cause your CO2 cylinder to empty within a week (and it becomes a hassle to refill it).
Unless you live in an air tight room, and you have several large CO2 cylinders (20 pounds and up), I would not worry about CO2 hazards under normal use conditions.
and I am also really worried about the end of tank dump so I would want a regulator that is well known and preferably that won't give me this problem.
If you want to ensure that you have no end of tank dump, then it is best if you look into purchasing a dual stage regulator (the Aquatek is not one).
So what does everyone recommend? so far my mind is thinking taking a chance with the Aquatek and a second hand fire extinguisher from ebay, and hopefully the USA regulator connecting to a UK cylinder/extinguisher.
As already mentioned, the Aquatek is not a dual stage regulator, and will not prevent EOTD. For the second hand fire extinguisher, just ensure that it has a UK standard so that it can be refilled. Ensure that whatever regulator you purchase also fits the fire extinguisher.
If you have not already, take a look at my primer to pressurized CO2 (linked in my signature below) for more information.