As others have said, plenty of other fish in the pond so if you are unhappy, by all means, I'd move on and see if the grass is greener elsewhere. Having said that, 1) the £15 service fee is not an error, it is chargeable for all cancellations before taxes are refunded and indeed surcharges are non-refundable, 2) none of what you describe is new or has deteriorated in the past 5 years or more - the service fee was there, the cancellations often not working was there, the non refundable surcharge was there, etc. So no, things have not "deteriorated rapidly", it just seems that for some reason you were lucky enough not to experience them before.

Also, I'm not sure you'll find alternatives more generous/selfless when it comes to refunds but it's obviously a good idea to try a few other options for yourself and see if you like them better. I fly with 20+ (often 30+) airlines a year, so I'm certainly not one who'd advocate putting all your eggs in the same basket if/when you find better deals elsewhere.