Also in Hertfordshire is a Citroen and Peugeot independent specialist called BL Autos http://www.blautos.co.uk/
. I have used them once for some small thing so can't really give a huge recommendation, however I can tell you they were so nice to me and didt charge me, that I ended up going back later that day to tell the owner what I thought of the mechanic who helped me and a bottle of nice wine for the mechanic as a small token of my apreciation.
2012(62) XTR 1.6 92bhp Airdream Modutop
Both the guys you mention are great, but tbh, the price from the dealers is quite reasonable if that includes a new dual mass.
Would be interested to see what the two other guys quote.