Are you talking PPL ground exams under the CAA/JAA system? If so then yes many people have done them in the UK before venturing over to the US to do an intensive 3 or 4 week PPL. Do a search through the private flying forums as its been asked many many times. Some UK schools will be quite helpful others will be annoyed that you don't want to pay them an outrageous amount of money and take up to a year to do your PPL with them. I have a vague recollection that there might be some online resources to help you bone up on the exams now in addition to the confuser publications that are available from pilot shops.