As did the motorised valve, thermostat and timer. I studied
unvented but after showering at a friends house I realised the
pressure was crap when compared to a pump.

But the performance of unvented depends on your local pressure and flow
rate. There is little point in looking at a friend's system unless they live
next door and have an indentical water feed.

I have used pumped, unvented and heat bank systems. Each one provided a
fantastic shower at high pressure, and not flow rate limited.

Christian.