I also had BT only on day 21, and i always ovulated on day 18 (big O pains). I think my first cycle on clomid was a bit all over the place though. Can you request another BT for day 21? I don't see why they wouldn't let you.
And my DH had a semen analysis done last year and it cost nothing up-front and then we got a bill sent out for about $50. I don't know where your GP got $385! What state are you in?