Well on balance and taking into account of the age and price of the car I'm feeling quite happy and reassured that the noise is nothing I can't fix myself for a reasonable price. I'm very grateful for the advice and thank you to those who contributed. The plan of action is now to drop the box, fix the crankshaft seal (£12 + the flywheel bolts), fit a new clutch and spigot bearing and hopefully things will be fine. The car is lovely to drive, she's not new and it's a lot of bang for your buck so to speak.