Don't ask me to quote specific law, but from memory the prevailing consensus is that they are entitled to refuse to send the records to you.
This is an area which is the subject of some lively debate among legal scholars. The reasons usually given are that there may well be information in the records which a doctor might - on valid therapeutic grounds - decide should not be disclosed to the patient. Of course, the decision on this issue passes from your old doctor to your newly nominated one.