I have the chance to purchase a VW Beach Buggy with no V5 or VIN number at a very good price. Is there any way apart from IVA that I can get it registered with DVLA or is it just usable off road or to break.

If it doesnt have a VIN or V5, its pretty obvious and other vehicle does...
If thats the case, then the car is pretty well worthless

Beetle vin number is normally on top of the tunnel below what would be the rear seat , I would have thought if it has a shortened chassis it would still be there ?

Personally I'd walk away and not get involved. If it hasn't got a VIN number I'm not surprised the price is "attractive". The person is probably wanting to get shot of it and avoid any bother. IMHO move on and find something else - more than plenty of cars out there!