Thanks Paddy, but the draught comes through the entire front of the box where the rows of trip switches are so I need to seal the entire front.
A few years ago we tried some of the expanding foam spray to to do the perimeter edges but that was a bad idea 'cos an electrician spent ages, trying to access the box and eventually had to crack the cover to get it off !
I put on the bubble wrap last night, secured lightly with duct tape, and I really feel it has made a difference I'm just a little unsure of the safety of using it...