emailed a few enquiries to local garages to see if I could elicit a cheaper, firm quote. Some said no dice, "we only fit our own parts". So not only do they want the labour money, but the parts profit to...I guess it's a business decision, unless of course they don't want to be held responsible for fitting dodgy parts...
One garage insisted on viewing the car first, to see exactly what work is needed. After a few swear words about how difficult it would be (!), they settled on a price of £200. Same garage that fitted my rear upper suspension arm 2 years ago! Since no more replies, I'll be accepting their quote.