This is one of those "if I had a pound" type questions, and firstly - what package a friend or neighbour gets with VM is certainly something to factor into your prep before negotiations, but becomes completely immaterial in your dealings with VM.
You need to firstly price up your chosen package of services as to what the standard price is with VM (i.e. the price after the initial promo period) and then the price from a competitor provider (Sky, BT, take your pick) for the nearest available package - and then you've got your pricing sorted.
Get in your mind a price that you'd like VM to offer "in an ideal world" in exchange for an 18month re-contract, and a price you'd be willing to accept. And go into a call with VM Retentions, with those figures in mind. You also need to be willing to walk away and give disconnection notice if you don't get a price you're happy with - if you're not (or the agent doesn't think you are) then you lose some bargaining power straight away.
That's the short version, longer versions of "how to negotiate a package deal" are available, this should give you a flavour. VM don't have a customer-facing CS email address, and the forum staff don't have a remit for package changes - you will need to call.
I'm a Very Insightful Person, I'm here to share knowledge, I don't work for Virgin Media. Learn more
Have I helped? Click Mark as Helpful Answer or use Kudos to say thanks