It's common knowledge that if you phone up and try and cancel a sky package they'll offer you a reduced price for a period of time as an incentive to stay or keep the channels you wanted to cancel.

So my question is, has anyone phoned up to cancel, got the reduced deal then called up a week or so later to upgrade to Sky HD

My plan is

Phone up to cancel the movies and sports

They offer me a deal for 6 months saving me maybe a tenner a month

I phone back a week later and order HD

So I guess I'm wondering if I order the HD which is about a tenner a month will they add that on top of my cheap deal or cancel my cheap deal and revert back to the full price and stick the HD cost on top of that?

Phone up. tell them its not working very well. they will say that it will cost you X for an engineer, tell them you can't afford it, pause, tel them you was thinking of changing, tell them you can't afford it, maintain politeness put phone down.
phone them a week later, to cancel, they will upgrade you if you maintain your poker face

What Steve said.

Used to work for them. Try to cancel, they will start with small offer (probably free engineer visit to fix it or 6mnths half price) and work up. Keep saying 'no I want to cancel my subscription' until they get to the level you are after. Maybe only try it once a year though.

have you got virgin media (or whatever its calling itself thisweek) available? Allways extra bargaining power

Or do as my daughters done, ring up and cancel then get your partner to take it up instead and get all the good introductory deals!