Which Service Centre? UK

Over Christmas took some photos of an impressive sunset over Snowdon from the top of the Glyderau with my 100-400 IS. As happy as I was with the pictures, I found it incredibly irritating to find loads of flaring caused by strong light from the sun being distorted by dust on the inside of the lens, ruining some of the best shots, and requiring some photoshopping on others.

So I've resolved to get my two year old lens cleaned. I've already dismissed the idea of sending it to Colchester Camera Repair, as their quote was for £180+VAT + return delivery.
Canon won't quote me yet, but have supplied a return code, so they'll take a look and give me a quote for the work (feedback on Canon repair seems very mixed).
Whilst Fixation also need to look at the lens, and Leihmans have quoted £120inc VAT unless there's some expensive parts are required - which provided there isn't anything other than dust, seems quite expensive...
I believe all of them offer 6 months warranty on the work they do.

Canon's service could be the cheapest, but there seems to be queries whether they actually do anything, or that they take a couple of weeks to repair, rather than the expected 1 week turn around.

So, the quesiton is - which should I go for? Looking for a balance of cost and service. Its not my main lens, but I don't want to be without my glass for more than a week or two.

When I broke (bent?) the front rim of my brick, it was away for exactly a month. I sent it via my local dealer to save hassle.

Lowner wrote in post #7023436
When I broke (bent?) the front rim of my brick, it was away for exactly a month. I sent it via my local dealer to save hassle.

A month? Were you happy with the results, and do you know to whom they sent it?

It was sent back to Canon. Yes, the repair was a total success. In fact sending it via the dealer was no more expensive, so I suppose Canon must do some kind of "commission". Either that or the dealer did it as a favour to me.