Ha, the awkward little gits!
Having spent time rehabilitating ferals myself, I must say this is typical, brings back memories!
I have a cellar with a window which used to be called the 'drop in centre'

Made it easier with food and water and a tray too although it ended up reeking of tomcat spray. Oh and one evening I got a litter of kittens delivered.

By their devoted Mamma, who's still with me.
Talking of kittens, what a randy little devil, and this I'm afraid could be serious - have you told the rescue people about this as it's quite likely she's pregnant now. Kittens are what none of you need. Could be a good idea to catch Mamma and spay her pdq. To say nothing of the great lover.
Is there any way you could obtain traps, from the RSPCA, from vets? I know how you must feel; it's very hard to go on pestering, especially when it's difficult, talking to people.
At the moment you may have to harden your heart, leave food out for say half an hour twice a day and if they don't turn up then, they'll have to wait ... I know, I'd hate to do that too, but ... They can be canny though; they'll learn.
Cats!!!
Again, all the best and looking forward to the next instalment.