Thanks Graham i value your advice mate , I dont mind lugging a trolley around for a bit ! I am getting a van mount with a 500 tank , so to add a trolley with a big tank make sense for me 
You have to see my work to appreciate what i mean 
If you are seriously going to get a trolley mate, don't get one any bigger than 50ltrs, anything any bigger would be near on impossible to lug around all day, and a big big mistake whatever your work is like!! You say you are getting a van mount, thats great!! you won't regret it. So why get a trolley? there really is no point, if I were you I would get a backpack to go with your van mount. That would be far more useful, and I am talking from experience here, I started off with a 50ltr trolley, and after lugging that about for 2 months I was ready to give up on wfp altogther, and I went back on the ladders for some time. I then got myself a backpack which although it was a pain having to lug it around and keep refilling every 20 mins or so, it was better and quicker than the trolley. I then got myself a 400 ltr second hand tank, fitted that in the van, took the pump off the trolley and made myself a van mount, the best thing I have ever done concerning window cleaning, and I haven't looked back since!!! I still use the back pack, very rarely! probably about 2 jobs a month it comes in handy for. As for the trolley, I slowly took it apart and used the bits for spares, and took the rest of it down to the dump!!!
Anyway mate whatever you decide to do, good luck with it!! But think very carefully before getting a trolley, bigger is definetly not better where trolleys are concerned!!!
