Subject: Re: Source of correct shade paint for heads and block
To get back to Laurence's original question - for the last 25 years I have been using Paragon paint for a number of engine blocks and cylinder heads in a variety of colours. I cannot recommend them enough; superb paint, totally heat resistant and available in just about any colour you want. Have them send you their sample sheet and you'll find a choice of almost 400 coulours including a perfect match to the original Staines engine block colour.
https://www.paragonpaints.co.uk/