Just thought I'd update this.
I've replaced all of the brake bleed valves and dust covers, then of course bled the brakes again with a friend (haven't bought a power bleeder just yet!).
This has slightly improved the feel, and I did notice a couple of bubbles come out, and I tapped the calipers with my new (stinky) dead blow hammer to help out. I went around a couple of times, gently topped up the fluid so as not to get any air in that end.
Of course whilst we did this the pedal felt amazing, then once the car was on the feeling was lost.
I did make a minute adjustment to the pedal, which helped out.
I'm wondering if there is still some bubbles trapped in the calipers or even the master cylinder, which perhaps the power bleeder may help for that
Sealey VS820 & VS820UA bought (plus a new master cylinder cap if the universal adapter doesn't work)
Hopefully it's just a case of needing to be bled a few times.