This is one part of aviation it certainly pays to shop around.
A Dr Jamieson did my Class 2 initial near Cumbernauld (with ECG) for £150 (outside normal office hours) a couple of years ago (I'm sure that price has since changed - back then he also charged £110 for a class 2 renewal).
Another Doctor in Glasgow wanted two appointments (ECG separate) charging £160 for the exam and £70 for the ECG so £230, so long as the ECG was before 4pm. If I wanted the ECG out of hours it was £875 (to book time at a private clinic)...