Can MSE discount Sky codes be trusted?

A question about : Can MSE discount Sky codes be trusted?

The Sky forums have many threads from people stating that the MSE Sky discount codes worked at the checkout stage but after the Sky account was created, the 12 months discount didn't apply or only applied for the 1st month. When they have rang up to complain they get told a 50% discount isn't available on the Sky billing systems. The Sky reps on their help forums say they need to contact MSE.

What is the process for raising a complaint when the 50% discount is not applied after the order has completed?

Thank you

Best answers:

• I had a MSE 50% off code over two years ago. The one year went through as expected, with the 50% off applied correctly. The tricky bit was the HD upgrade, which was not part of that promotion. Luckily, I found a separate 50% off promotion for HD upgrade, so that was good. Cancelled after a year without penalty.
  The most recent MSE deal is 40% off with code.