As a long time Landlord, I can only suggest that the operation of the boiler is simple, the filling loop is in position and carefully explained to the tenant on how to use it when needed. I have not had anymore problems with Potterton than any other make of boiler used (Worcester Bosch).
If you have only the one tenanted property, you could ask BG to take out one of their monthly payment agreements. It will give you an annual Landlords safety certificate and service. There is one that includes parts and labour for breakdowns etc. as well. All costs offset against your rental income of course It seems expensive at the time, but when you are called, when on holiday, tenant without hot water, it is worth doing.
If you have only the one tenanted property, you could ask BG to take out one of their monthly payment agreements. It will give you an annual Landlords safety certificate and service. There is one that includes parts and labour for breakdowns etc. as well. All costs offset against your rental income of course It seems expensive at the time, but when you are called, when on holiday, tenant without hot water, it is worth doing.