Should I change instructors ?

It depends. Are you attempting to blame your failure on your instructor? Why did you fail your test?

IMHO, I understand people who fail the test due to nerves. However, I don't think nerves warrant 5 majors (with the 8 minors too!). Probably a bit irresponsible on your instructors part to put you in for a test that you're not ready for.

Absolutely, your instructor should not be aggressive with you. That's unprofessional and counter productive.

Today I failed my first driving test today with 5 Major faults and 8 minor faults, have done 30 hours with my instructor. Is this a sign that I should consider changing instructors? He also is very aggressive, he keeps telling me he can't teach me anything else because it's all mental and that I need to do what I learnt?

Serious Faults - 1. Observation left-hand reserve ( I was waiting for vehicles 1/2 mile away but the road was 60) 2. Change in speed 3. Signal ( was in the middle lane last min he said RIGHT here, so drifted but forgot my signal due to the panic) 4. Undue hesitation ( Missed a gap going into busy main road, there was no box in the middle to wait when turning right. I need covered this in road or situation with my instructor) 5. Too close to a parked car mirror when moving in to stop (this was right after a busy mini roundabout, he said pullover on the left but i didnt hit the mirror.

Also 7/8 minors where for progress