Yorkie, the difference in readings is most likely down to the accuracy of the two gauges - there's no obvious reason why they should be different, other than the one in the loft possibly being at a lower pressure 'cos it's physically higher up, even tho' it's a sealed system. But, you do need to get the system down to a sensible level, and that's around 1.5bar in your case. Just keep bleeding - it will fall. And - yes - that is 'cold' pressure. It will likely rise as the system heats up, but I wouldn't worry unless it goes over 2bar (ideally it shouldn't fluctuate much at all, but in practice it can do, especially if the system is on a few levels.) Next step is to NOT replace your mixer shower with an electric one. Electric showers are awful, especially in winter. Combi-driven showers are superb - as much hot gushing water as you could want. And you are thinking of removing the remaining 'good' thing about combis?! Seriously - you'd be as mad as a Mr Hatter to swap them. Your new combi should be reliable, so don't worry about it packing in any time soon... That leaves the only 'real' drawback, that of slow bath fills. There is no solution to this other than giving yourself 10 more minutes. Accept that - and be happy.