unless your doing big stuff like plant machinery and artic trucks and stuff then you wont need to mix the tfr.
just get yourself a hozelock from makro/b&q and put some tfr diluted 1-5 in there wet the vehical and then spray on,sponge/brush and jetwash off
with regard to the watter tank you could get a flat baffled tank off ebay your looking at about 250 for one or if your on a budget you could go to your local plastic recycling plant and they normally will sell you a washed out 205l drum for about 8 quid and 200l will wash around 5 cars.
hope this helps if you need anymore advice just post with heading valeter and i will get back to you i'm on most nights
also talk to your local autosmart dealer they will point you in the right direction with regards to chemicals and things