thanks for the replies - i met with a pool firm yesterday and they are in fact recommending an in-floor cleaning system. . This would feed the heat (from a heat pump) in from the bottom and they claim is an efficient way of heating the pool. only concern I have is that this means little pop-up devices around the pool which presumably could get broken. I'll let someone else be the guinea pig with in-floor heating, I still reckon with a good insulation beneath the concrete this could work!
The pool will be a freeform of 9m by 5m, I have an indoor endless pool in my uk home and I will probably fit the same swim current system. I was thinking about a 15mtr lap pool but in the end I figured a smaller pool would be cheaper to build and run and hopefully look nicer.