I ended up getting 30mm mild steel tube from FH Brundle at £19 for 6m and they cut it for me too 
Delivery would have been expensive, fortunately I live minutes from the Ilkeston branch.
However I do wish I’d got conduit instead because it’d be galvanized and I wouldn’t have thought to myself … “Hmm, this is going to rust. I should maybe paint it.” This probably has gone without saying so far. Do not (once again do not) do this - or if you do, don’t imitate my crap job with a rattle can, might have been okay with black etch from a proper spraygun if I’d been able to get in the booth at work. Cue much sanding to get it back smooth enough to not snag the bearings 
Doh!