Updating uk maps on old TT one v2 ??

[will4]

Hi, got an old TOMTOM one v2 sat nav unit uk here that I have never bothered updating any off the maps since I bought the unit many years agao and just thought it would be nice to do an update now with so many new roads, streets etc , just a bit confused on what the best way to do this is ?? how much would it cost me to update the uk maps on my unit ?? can I buy a new sd card containing these updated maps at a cheaper price ie thru ebay etc ??
any advice would be much appreciatted.