sky+hd box isnt getting a satellite signal?

It will either be the dish (unlikely but possible) - fallen off wall - moved - snow - wind-blown debris - silly reasons.

Or

The cable from the dish to your sky box - particularly the connectors - disturbed by moving your Christmas Tree perhaps.

The Sky box itself may have gone on strike but check the connectors first.

Good luck...

Peccavi
January 2013