I've emailed Cyclefit and explained the situation, but they basically are saying that that's the way they do it and if I had wanted it different I should have specified!
That's your case & claim in a nut shell.
You need to put it in writing
to them (not email) that you did
specify the height & cut to be undertaken (i.e. to the minimum requirement) & anything else done by them deviating from that requirement is incorrect.
As innocuous as it sounds, you can then contact some like http://www.citizensadvice.org.uk/
to provide advice on the workmanship undertaken & to provide recommendations to the retailer that a refund is in order. Once you have someone of 'authority' backing you up it would be rare / stupid for the retailer to hold out. If they refuse at that point you can kick off a small claim.
Make sure you keep everything in writing from this point & keep things amicable but firm (not like this... viewtopic.php?f=14&t=103189&hilit=time+pedal
). Emails just don't have the firm impact that letters do & are much more firm as a reference point if to be relied upon at a later date.
At absolute minimum you should press for the work done by them to be refunded (which you should be able to get back - I assume they built the bike for you?) & beyond that look for recompense on diminished re-sale or usability of the frame to you (this is a tricky argument tbf as the utility offered by the frame isn't actually reduced, its just aesthetically affected).
You need to push the fact that they hold themselves out to be a premier fitter / mechanic & thus more professionally competent to undertake the specified work than anyone else, thus making the error on their part all the more onerous.