I just wondered what qualifications would i need to become a peripetetic music teacher in a school? Do i need a diploma? if so does it matter if its a performance or teacher one? What level of diploma do i need?

There's no gold standard here. If you want to work through your local music service you'll probably have to pass an audition so they can see both your playing skills (at the very least Grade 6 level, hopefully higher), and show evidence of a music degree, teaching certificate or diploma. At the audition you may have to demonstrate your approach with a total beginner. If you have a diploma you're basically laughing.

If you want to work directly for a state school, it's up to the individual discretion of the school, though the more relevant music-related letters after your name the better. Or evidence that you're a successful working musician and can teach too.

If you want to work in a private school, you'll generally be up against other applicants with diplomas so there's probably not much hope there unless you've got one. Having said that, they probably won't know the difference between all the various diplomas - anything with the word 'dip' in it will most likely impress. Unless you're up against other dip holders, in which case they'll go for an instrument-specific teaching dip if they've got any sense.

Violinia

It depends what school you want to work in.

I know that when I've seen applications people put down all their instrument experience, and if they have any other experience of teaching. Some have things like a CT ABRSM under their belt as well.