Thanks to everyone on here that has offered advice etc. It's been very useful.
Sorry I haven't thanked or responded to every message - didn't want to fill the thread up with countless thank-you's etc.
Decisions made so far.
I've ordered an extreme brush and carbon fibre gooseneck from Gardiners to replace my superlight and metal gooseneck. As it's a quick-change brush system I've also ordered a multi-angle adaptor to suit. So... that's a bit less weight to move around all day.
Next thing was to make a temporary change to my trolley so it just worked as a pump box. The inlet pipe is just swapped from barrel to to barrel as required. Brought the heavy duty reel and microbore hose out of hibernation.
So today went like a dream - no lifting the trolley in and out or lifting barrels.
Will try this system out on a few more rounds and if successful, I will buy a 210 litre flat tank and make up a pump box with items I already have in stock. The trolley will still be required on some jobs but I will buy a 12v bilge pump to fill the trolley from the on-board tank as required.
The final outcome will be a sort of 'van mount system' with minimum outlay.
Thanks again to you all for getting my grey matter working again.....

John