I had a really annoying squeak that was coming from somewhere on the car and came and went a bit but was there more often than not. Have traced it to where the passenger lower dashboard panel sits over the chassis frame immediately above the passenger's knees. Have stuffed in some rubber decorative leaves from Xmas card manufacturing kit for the kids and the squeak has disappeared.

Might sound trivial but the car is transformed. Car feeling great now with almost 800 miles on it and goes in for 1000 mile check and oil / filter change tomorrow. Hopefully I can then regard it as sorted.