Sky are doing an offer where the longer you have been a customers of theirs the bigger the discount you get on the Sky HD box.
If you have been a Sky TV customer for:
Up to 3 years: £279/419 (saving you £20/30)
Between 3 to 6 years: £249/369 (saving you £50/80)
Over 6 years: £199/299 (saving you £100/150)
https://hd.sky.com/thankyou/