Horses for courses people.....I would always fit genuine but, its better to fit a cheap pattern part than not fit anything....
That's right, Mark. If I were single with no kids and a facelift 3.2 MV6, I wouldn't dream of getting anything else than genuine parts. As it is, I've two kids and a 1995 2.5..... The car's market value is probably no more than £600-£800 and I reckon I've spent that amount this summer just keeping it going! It doesn't mean I don't care about the car, though. I still have a soft spot for it. Going cheap in this case is a bit like treating your other half to fish and chips rather than a la carte at the Ritz.

(Not a good analogy, I know!)
As you say, better to fit cheap pattern part than leave it as it is.
BTW. I've just found a place that does a Timax rear box for just £26.73
http://www.onlineautomotive.co.uk/product_details.php?part_id=49601&type=part&table=1