As above who,are you talking to ?
Morrison's will pass this to their insurers who have to deal with it.
Morrison's will not pay direct to you. You have shot your self in the foot here , morrisons agreed to pay the insurance cost of £600 but you have gone and done the repair your self by getting another wheel , this invalidates the claim .
You should have collected the £600 and only then got the wheel for £50 , you would have been £411 better off but you have blown it.
Hope you have not told your own insurance about this as if you have they will now give you a loading for having a 'claims history' and your insurance for the next 5 years will be double or even triple .