Thanks very much guys, i know you'l laugh but staying with barrels,
reason being my ro setup is at my parents in their garage at end of shared drive difficult to squeeze van down there and parking can bit a pain at times (parents don't have paved drive)
So if tank in van would then have to run hose pipe out of garage into street to van

Not good idea especially at mo with hose pipe ban :

Daz, how did you find the leaving trolley on van?
I remember you were quite concered about getting close too houses. (like i am

)