Having been associated with the Heating & Plumbing Trade for some 40 years I too don't like Combi Boilers. Give me the Traditional Free Standing or Wall Hung Boiler. But having said that one of the most important things with any Boiler is regular Annual Servicing by Fully Qualified Gas Engineer who is registered Gas Safety if in doubt of his qualifications ask to see them.
I don't like combi jobs either, currently using a Worcester free standing oil boiler which is regularly serviced by the manufacturers maintenance programme. Friends and neighbours who have gone down the combi route report mega bills and rubbish reliability
What bothers me is the requirements when I come to replace it. Any idea I can just get a simple replacement are negated by current requirements
I must admit it is difficult these days. One of the troubles there are so many new regulations, and a lot of the so called Heating Engineers and Service Engineers don't really understand them. In some cases they will not look for what the customer wants because its less money and they go for the big Bucks. Actually I'm often (at least once a year) when he services my Boiler. Apart from doing my Heating and Servicing work he is also a friend I have known for some 20 odd years. Will have a look around for you if you like and see what's available in the Oil Market.
In actual fact my Worcester jobbie is no more than 5 years old and, with proper maintenance, will probably last for a good few years yet
However, my daughter has a glow worm gas thing on the wall which is now 11 years old and I fear it will be impossible to replace it with a like for like when it goes to boiler heaven. As you say, the real difficulty (apart from the jobsworths and their regualtions) is finding some qualified guy that knows what he is doing
What prt of the Country do you live obviously I'm not asking town etc just South West North West London etc I might be able to put you in contact with a reputable man or Company ? Will have a look so its Wall Hung is it Conventional Flue (ie: Flue goes up out the Roof) ?