Thanks for your input chaps, bit tricky trying to drive Morgans with tuned up engines! Don't want to waste a salesman's time by testing a 3.7 either. L
Luckily, I own a car dealership, and don't have to worry about labour costs or VAT (until I sell the car at least!), but even still, I'm expecting a bill of around £6k.... not bad if you consider the price I paid for the car, and what a 3.7 Roaster would cost.
Have emailed Simon, and look forward to his advice.