Find who your MP is and email address here
members.parliament.uk/members/commons
I suggest something like this:
Dear Name of MP,
Next week you will have a vote on whether (area where you live) will move into Tier (what tier has been proposed for your area). This will have a devastating effect on the lives and livelihoods of all your constituents. Have you seen evidence of a cost benefit analysis for each of the proposed measures showing that these measures will not do more harm than good? If such evidence exists it should be available to the public. If a cost benefit analysis does not exist then it is your duty to vote against these measures to protect your constituents from unassessed damage.
Kind Regards