Finally had all my tools in one place to be able to try and bleed the last little bits of air out of my new caliper. Followed
@Yellow fr 's advice and lots of air came out of the nearside rear, but after doing the other calipers and pumping the pedal to let the pistons adjust, the pedal will feel soft on the first push, but then hard on the second.
At the moment, I'm probably just going to go out and do the same again tomorrow - remove the caliper and wind it back with the bleed nipple open - to see if I can get more air out, but it's always handy to check to see if anyone's had the same
problem and knows what it is.
Finally saw where my ARB bushes are when I had the front wheel off. That's going to be fun...