Having now had my crossflow looked at it appears that I need:

New Cylinder Head (currently Burton st3)
711 Block
forged pistons + all the bits

or is there an engine out there available I could transplant?

Stick in a 2.0 Zetec. They cost peanuts to buy and generally totally reliable. Even as standard they produce more power than a all but the most expensive all steel x-flow and offer far better drivability.

I accept that the fitting costs a few pounds but there are many more bits out there now than there were when I did it at much better prices.

Much as I love x-flows (had them in cars since 1974) its just not worth spending good cash on them now unless racing regs insist on total originality.

Good news: I have a 1300 block you can have for free...... Bad news: It is in Kansas City USA!!!!!!