Sorry you've been treated like that by GP's, there are some crap ones out there unfortunately.
The chlamydia test thing is to do with something called QOF which are targets that have to be met. They're obviously realising it's coming up to April and they haven't done enough. They shouldn't be forcing them on patients though.
If you've already written to your Practice about the Doctors you can write to your local PCT or CCG (Primary Care Trust & Clinical Commissioning Group). I've done it a few times about Practices. You could PM me your local town and I could find out who you can write to if you want? (I work at a GP so I have my ways
) If you have copies of your letters to and from the Practice you could send them with it and they will do an audit on your record and look into it for you. They've helped me a few times.
What did they say back to you on NHS Choices?