ive owned the previous Powa model from the 1990s - however the one you have is one of Vax's later ones and aren't as well built IMHO. Benny/VR and BEKO would also be able to give you info here as they have had Vax models like this in the past.
Vax canisters all have 32mm measurement which means you can use any tool from Numatic, Hoover, Electrolux and other brands that still use that sizing.
However they're not bad at washing carpets even if the set up is a long drawn process. IMHO the original wash heads are far better than the ones Vax now supply because they are simpler and better made.
Also if yours doesn't have a variable suction control dial by the handle, the dust bags are liable to burst open due to the fixed suction. Best to get the washable, reuseable fabric dust bag if you are going to use this vacuum for dry suction only.
They're far better as wet and dry vacuums and can be used bagless, but then at the detriment of having to unclog the central filter.
Only thing I don't like about the Vax canisters is that they can tend to fall over because of their narrow/tall height compared to Henry.