I'm hanging on to a bit of hope. The water is a bit warmer. No idea what is going on, but in principle things must be working for the water to be heating and flowing at all. Wondering if thermostat dodgy (coupled with the -5 weather temps meaning cold feed is cold -I did say I was being hopeful
) Still very concerned now is the smell in the cupboard with the boiler. I've checked outside, and the flue is 'puffing' so not blocked and the plumber fixed the leak they caused on the boiler (smell was only there after initial repair but before he returned and has continued since). Plumber claimed he couldn't even smell it, but he's the only person to say so! Pic of pump I'd taken earlier.