Hiya Stuart
I helped pack your system myself.
The pipe is quarter inch. The RO comes with about 2 metres of each pipe needed as standard. I put about 30 to 35 ft extra quarter inch pipe in with your stuff along with a connector. The extra pipe we supplied you is very good stuff and wont kink easily at all. I think that if you are carefull when laying it you should be fine.
Very good idea about putting it into that other pipe with insulation by the way.
I wouldnt mind a pic or two of this being done.
Hope all is well with what we talked briefly about the other day mate.
Cheers
Andrew