When you say 'being crap about it' do you mean they are moaning slightly (absolutely fair enough) or moaning going on and on (perhaps a bit grating, but not too much of an issue) or demanding compensation (not so clear cut)?
You sound like you've been a decent LL in the past to them. That's good and it's something they should be able to expect as standard, not be seen as super kind treatment. However, I do agree that as in all things, a relationship develops and there is a hit if give and take and goodwill and understanding involved. THe Op was understanding about the wipes blocking the loo and sorted the problem. She could have charged them and didn't. The boiler issue is a pain and they are due to have access to hot water etc but as others say, she can't wave a magic wand and this kind of repair can take several days - it is a nuisance for the tenants, but it is one of those things. Other things might go wrong too - it just isn't possible to instantly fix them and people have to expect a reasonable wait. The question becomes what is reasonable? Once it goes beyond reasonable then I think compensation is probably needed, but it's not needed instantly. If OP has provided plug in heaters and kept in good contact and the issue with the tenants, then I think she is fulfilling her role.
No one is ever going to be pleased to have no heating or hot water. The OP needs to be very sympathetic and to apologise for what has happened,mbut also professional - accepting that these things happen and being clear that she is on the case and keeping them updated with what is going on. However, there is no need to grovel and self-flagellate over this. It is one of those things that happens and if the LL handles it quickly and professionally, tenants (like homeowners - and just because you are a tenant and not an owner doesn't mean you can expect miraculous repairs without any time delay) just have to accept it as one of those aspects of living in any property.
LLS need to behave responsibly and quickly. Maintaining goodwill is always important too. Apologising, acting quickly, being a bit flexible, perhaps taking some wine or flowers on the day of the repair is all good. Being willing to offer compensation if the repair is significantly delayed would also be good, but isn't needed for a few days.
And OP, you need to get used to showing goodwill and not always getting it back. It's the reality of the market. People want you to be flexible with them (the toilet) but forget when they want something. Set yourself high standards and don't expect too much goodwill in return and you'll be less disappointed. And have confidence in yourself and your response if it is speedy and reasonable and accept that repairs will occur and can't happen instantly.