Broag remehas have very good manuals and schematics for learners to use and 5 yr P&L warranties, a good selling point, I personally hate worcester manuals which dont seem that clear as they are overcomplicated to my mind and only give a 3 year warranty unless youve done the courses with them, intergas are a good boiler as well with some good selling points ie no diverter valves to fail, Baxis good for mid price boilers and choose your cheap option at your peril,some customers will force you to put in rubbish at times
Have a chat to localplumbers and find out what has been put over the last few years, down here its the old baxi 105s and 80s
so if you learn how they work and install something similar your life becomes easier over time ( no need to mention that the newer boilers dont compare to the old ones, I was just saying fit what the locals do and youll help yourself a bit over time)