I have just replaced my 20 odd year old super reliable fantastic back boiler for one of these so called modern wonders (haha) combi boilers. I was advised to due to energy efficiency and running costs and I also struggled to find a gas safe engineer to service old boiler as younger guys now are not trained to service them. so I thought I'd go ahead and modernise and my god how I regret it! so much so I could cry it feels like a total downgrade compared to my old mid 90s backboiler. Running the bath takes a good 20 minutes or more longer, water no where near hot enough for a decent bath as boiler will only heat up to 65 degrees and by the time the bath is filled its going cold. we are a house that absolutely loves and needs baths to help with the aches and pains I suffer from. the central heating seems to work OK but to be honest I think old boiler kept the house consistently warmer and as for running costs I've noticed no difference at all as yet (according to my smart meter readings). no idea of the reason for my long post sorry, I just wanted to vent but if anyone does have any ideas of how to improve my bath water other than boiling the kettle! then any advice welcome. honestly feel I've just totally wasted £3000 to downgrade.