Power engineering do the 1.6 overbore and stroked crank conversion and it takes it out to just over 1.8 but they call it a 1.9 and branded it as system2 for some reason.
Vulcan engineering on the Uxbridge road in Hanwell also do these conversions and were infact supplying PE for while

185 Uxbridge Road, London, W7 3TH.
Tel: 0208 579 3202 / Fax: 0208 579 7390