Because you are going to continue using the thermal store boiler efficiency is negated and therefore shouldn't be top of your list when choosing a boiler.
If you fit a system boiler the warranty will obviously cover the pump aswell. Whereas fitting a heat only if the pump fails you will have to pick up the bill. It's not really a big thing though.
You can fit literally any boiler brand you like, they all have big warranties and are much the same. The hardest part is finding a decent installer, it's generally best to find the installer and go with their recommendation.
The Baxi 600 series boiler is a good all round. Vokera also a decent budget boiler.
If you fit a system boiler the warranty will obviously cover the pump aswell. Whereas fitting a heat only if the pump fails you will have to pick up the bill. It's not really a big thing though.
You can fit literally any boiler brand you like, they all have big warranties and are much the same. The hardest part is finding a decent installer, it's generally best to find the installer and go with their recommendation.
The Baxi 600 series boiler is a good all round. Vokera also a decent budget boiler.