Always the best idea Jim. I do test pieces for most things I do paint wise, not just to prove the finish is what I am after but also to check compatibility. Sometimes the time between coats is very relevant as well and, if proven by the test piece, should be repeated in the actual work. i.e. if you leave a base coat for a couple of days before applying the top coat on your test piece then repeat this timing when you do the actual paint job.
I’ve been convinced now for many years that some declared paint incompatibilities you see on line are as a result of not waiting long enough for all the volatiles from previous coats to have completely evaporated. Not a guarantee but a point worth remembering.
And I’m with Colin, Halfords satin primers in black, grey and red are excellent paints and I’ve used them on many a model! This is just one. Please excuse the washers around the port holes I didn’t build it!