This sounds horribly familiar,
When I completed my first Class 2 Medical I was referred for extra tests, obviously I tried the NHS but they kindly informed me it would have to be done privately.
For the 24 Hour Holter / Stress ECG / Echo-cardiogram it cost me approx £900 including doctor / hospitial fee.
For the Adenosine test it cost approx £500.
Once the CAA had all the reports it took approx 2 months to have my Class 2 issued.