Prices will always increase unless you regularly renegotiate your deal. If you did this now it would no doubt include an upgrade to a TiVO box, & an upgraded Superhub if you have Virgin Broadband. You can have a VHD box on your current deal for the same rental plus a £20 postage fee for the self-install kit.
Your best bet is to call the Retentions department (150 option 4 then 5) & see what they can offer.