Cheers K5!!

as a last resort if you cant turn the engine by hand... tow the car on a rough surface (not tarmac) with your foot on the clutch and try popping it in to fourth (as this is the strongest gear) brutal but sometimes works and if youve got to that stage the onlt alternative is a strip down anyway!!! worst case you bust a ring... this has freed of a couple of engines for me over the years.

if it does free put more diesel in and tow it around with the plugs out to clean the bores then put the plugs in a tow start (you will have low compression till it warms up and frees the rings so the starter prob wont hack it)