Thanks everyone. I am pleased to report he didn't charge me anything. And as I had supplied all the big bits he wasn't out any parts. He had offered to pay for the second set of gel pads and bar tape, so I ate the cost of those in exchange for the parts he had supplied (aero bars, cables, barrel adjusters and power link for the chain).

My short test drive back to the office suggests the conversion is a good fit for me and has resulted in a very comfortable riding position.

In future, I would love to do repairs and alterations like this. I'll have to buy some tools!