Another update.

Started to carry out a full detail of the car today, and finished today off by applying a good coat of nut oil to ALL the black bits again. This time leaving it overnight.

Tomorrow, I'm gonna take the nut oil off with a damp cloth rather than the hot, hot, hot water Mark suggested. Then apply the Auto Glym stuff using Fiona's suggestion of dipping it in a bucket of hot water.

Then it's onto the wheels. Take them off, thorough clean inside and out then put them back on - obviously.

A.