[Tannaton]

Unfortunately this is by far the most common cause of early death of a D5 - the AUX belt going and taking the timing belt out with it.

If the sound of the engine turning over on the starter is now a continuous whine like a washing machine then you have Valve and cylinder head damage. Often these can be fixed with a new/re-con cylinder head - however I have heard more than one story where an subsequently rebuilt engine has once again thrown the belt later in life, so I would look at a replacement. The labour cost of taking a head off is quite high so there really isn't much of a saving.

There used to be a company in Huddersfield advertising used engines on e-bay for a fully fitted inclusive price but I can't seem to find them. The D5 is so reliable that used engines are available at reasonable cost.

As has been said probably the most costly thing you can do is sell the car "as-is" and buy another.