Sorry to resurrect an old thread but realised I hadn't actually posted the final update on this.
I ended up going with a rebuild from TSR Performance (ZRP rods, Wossner pistons, R8 springs, Supertech valves, freewheel sprocket and a new crankshaft (mine was in bad shape)).
Shipped them the engine and they shipped it back around 5 months later. Sent it March got it back in August.
After a few painful weekends with coolant leaks and noises I didn't like, had it back in running again.
All in cost... a small fortune- more than than the car will ever be worth!
Ended up getting new injectors, coils, alternator, thermostat all sorts of other bits.
I think fair to say I didn't appreciate the scale of the job I was taking on, and all the tools I had to get hold of to do this job in the car park of my flat!
I've done just over 3000 miles on the new motor now, including run in, and it's not skipped a beat. Runs lovely!
Looking forward to eventually slapping a bigger snail on it as should be good for big power now!
I'm not going to pretend this was a reasonable financial decision but it's made me very happy!
Now it's capable, I can't wait until it's actually fast!
For those interested, the build was just over £5.5k. Shipping plus all the other bits I bought, total cost was around £7k and a bunch of my time.