Have you just Googled Manchester Vax and landed here?
Its a popular mistake searchers are making.
The reason you cant find them is because of your spelling. You should have searched for Manchester Vacs instead.
If you are looking for their website you can find it here: Manchester Vacs – Dyson Specialists.
Manchester Vacs are prevented from using the Vax name because it is a trademark of a brand of vacuum cleaner. For the same reason they are not called Manchester Dyson.
Manchester Vacs – Dyson Specialists
So now you know!