Depends what you want really. Screwfix do 10 downlighters including 2.5W LED bulbs for £80, so for two packs of ten plus two odd ones you're looking around £180.
The quote you mention seems high, but it depends on quite a few things, such as the quality of lamp and downlighter that the quote provides for, as well as whether the downlighters need to be suitable for bathrooms or look ultra-premium.
Expect about a fiver per lamp from the likes of LED Hut, with extra cash rebates usually available from Quidco etc., as well as discount codes from the site itself.
Assuming £5 per lamp, 22 bulbs would cost £110, leaving £170 for the actual holders. This is massively more than I'd normally expect to pay for 22 downlighters (excluding bulbs) from Screwfix, subject to quality, brand, whether it needs ingress protection ratings, etc.
At the super budget end, Screwfix do 10 x downlighters with LED bulbs for £80, so you're looking at ~£170 for 22.
As for dimmable, add about a quid per bulb and Screwfix do dimmable Varilight Pro (LED-friendly) jobs for ~£20 each.