UK car crankshaft and oil seal

Kia Venga Auto - 11 years old

Basically my car was struggling to start and took it to a few garages but they couldn’t figure out what the issue was. Took it to a Kia garage and they’ve diagnosed the problem that there is an oil leak coming from the bell housing area. They removed the crankshaft position sensor and found it’s contaminated with engine oil. The vehicle requires a new crankshaft position sensor and a new oil seal. To carry this out the gearbox will need to be removed to the affected components and to clean the area of oil contamination.

I’m just asking if people had ballpark figures of how much this might cost? I have a price from Kia but I know they charge more for labour. I’ve called around a few garages but they either can’t do it or I’m waiting back to hear from them.

Just thought I’d ask people on here for some advice, thank you!