In reply to iamaclimber:
I wouldn't do this. Seems a great way to destroy otherwise useful maps since 10 to a penny, the area you cut out and laminate for this weekend, WONT be right for next weekend and you'll end up juggling between 2 laminates sheets.
Better idea as someone above suggested would be to buy mapping software (Memory Map, Anquet etc) or subscribe to a service like OS get a map or grough route. These will all let you print off the exact area you want as often as you want. It also allows to you do stuff like print at 200% scale, which doubles the size of your 1:50k scale, which I find helps for fiddly or congested nav areas.
You can also print out a large sheet at 1:50k scale, and on the flip side of the laminate have 1:25k, 1:12.5k etc sections for any areas you'd appreciate the additional detail on (or even print a Harvey map back to back with your OS).
Much better approach than butchering your OS map, and you can then still use the full size OS map for planning long routes etc where its handy to be able to see the whole sheet.
Cheers,
Stu