For repair Rob you could try
this company based near Southampton. They're not brilliant, taking two attempts to replace a shaft seal for me but their rate was reasonable.
A Google search should find you a reconditioned exchange unit or book a mobile specialist to source one for you and fit it.
But before you do anything I'd urge you to be absolutely sure that the diagnosis is correct. A disintegrating crankshaft pulley on the diesel engine is often incorrectly attributed to the air conditioning compressor.
Simon