Cats started to bite and enforce mating - what now!? 10 points?

[fresha_k]

I have 2 cats - brother and sister both 1 yr old. I have always presumed they were spayed and neutered but (in hindsight) the guy we had them from probably just said that to make a quick sale as he lied about them being wormed n flea-ed.

Basically the male cat is now running up to my female cat viciously biting her neck and trying to mount her. So far I've been shooing him away but he is very persistent.

Anyway - how soon can I get them both "done" (can I drop in the vets? If not what will I do whilst waiting for an appointment?) and is there anything I can do to calm his urges? They usually sleep in the same room - what shall I do tonight? Seperate them or will that be worse?

Please can you give me as much advise as you can as I'm very worried for my girl cat. She seems to be presenting herself but is meowing and very frightened of his advances.

Thanks in advance
Yep he's got balls - I didn't ask if they had been fixed, I said that it is now clear they have not been fixed.

They have had check ups but I haven't had them for a year. I'm not neglectful - just need advise on getting them done and what I can do in meantime.

Thanks for all other responses so far

[Jarrod]

Separate them best you can for now. Most vets should be able to get you in a day or two. If you want a cheaper experience you may have to look up a strict spay/neuter clinic that will take a lot of cats in at a time, youll bring em in in the morning, take em back in the afternoon.