What not to do ? - If the cheque is from a business get it lodged, in case the business closes down. Without knowing the amount and the frequency you migh have to enter into sterling transactions, you might want to open a sterling account.
An option could be would be to ask your Bank to negotiate the cheque and ask them to hold the funds on your behalf.
I'm not sure what your desired rate is for exchanging same, but you will be faced making a decision sooner rater than later,