Thanks everyone, great comments, and I've made a decision. I do need to raise my prices but I'm going to be selective.
There will be a £1 increase on all the jobs obtained in my first year to bring them in line with my newer customers. All other jobs will stay the same as I'm happy with what I'm charging them as they amount to a good hourly rate.
I'm not a greedy person, I just want to cover the rise in fuel costs etc and earn a few extra quid.
I'm not going to raise by x% as this would mean lots of change and faffing about and I like the easy life, thats why I'm a window cleaner

Thanks again, I must post on here more often!!!