Cheers lads for more great input!!
I spoke to my fathers Ex-head TVR Mechanic, he said
"You've definitely got yourself a can of worms there...
I suppose to start off you could try and extract the remains of the bolts from the crank. To do this it would be important to drill into them correctly and so I'd propose a little drilling jig which could be made to just locate into the thread holes (it looks like that's possible on all in the pics) and then drill centrally through each bolt with a small drill - but important to use HSS not shit carbide drill bits!
Then you'd enlarge the holes to a convenient size to suit the largest screw extractor that will fit. With all extracted you can bolt in a new flex plate (flywheel) using new bolts and suitable grade of Loctite then another torque converter. The crank does look damaged but the area is normally a low stress area and also normally very over-engineered so unlikely to fail. However, I'd need to look in the flesh to be able to offer a full TVR A23 warranty on that
Should you elect to remove the crank, I'd not recommend it in situ' as the scope for missing things, dirt ingress and problems later are immense. The extra work would be well worth it unless you're outing the car soon after fixing it and don't want to waste time and cash..although having spent money on the head I'm guessing you're keeping it?
Obviously if you can't extract the bolt remains for whatever reason, you'll have to remove the crank. Sorry if this all sounds a bit circular - to some extent it will be as the job could and likely will evolve..be prepared!"
Anyway guys im going to start the project in Spring (as I have no garage space available!). Ill try to keep you guys as informed as much possible with progress!
Thanks guys for such great feedback! It fills me with confidence that perhaps she will be running and kicking down the road again! xD
Cant wait!! Cheers!
Rob.

Hi Robert,
I had a very similar problem to yours on a Ford Transit minibus many years ago.
Ill bet it all looks far more dramatic than it really is.
As said by alank46 and andyB, etc, get the bolts out, clean up all the burrs with a fine file, get new bolts and dowel pin. If the holes are really really badly damaged, they could be Helicoiled.
Degrease it all well with brake or fuel system cleaner, get some Locktite Bearing fit or Liquid metal apply liberally, and put it all together and stop worrying.
Do the bolts up to correct torque just check flywheel is running true. I would also replace crank seal as well while it's accessible.
If, unfortunately it did fail soon, then you havn't spent a fortune. If you start thinking about replacement cranks/or re drilling(which I doubt it very practical) the costs can spiral.
The one I did lasted with no problems at all for a further 148,000 miles until it was scrapped because of body rust
HTH
Roger