There are lots of good modems that are more modern than the HG612, so the Vodafone random one is not your only choice.
I use a ZyXEL VMG 1312-B10A, which is superb. However, I am on a slow ADSL2 link, so not a valid test relevant to your case, but lots of kitizens use ZyXEL modems and swear by them and some presumably use VDSL2 / FTTC. Those modems are not being made any more but new ones can still be had on eBay although they are horribly expensive as they are so very sought after. There are other ZyXEL wireless modem router combo devices available, which are presumably just as good in terms of modem performance [?] and are still currently being manufactured. I am not sure if the newer and cheaper VMG 1312-B10D is inferior in modem performance on a short fast FTTC line, but it is supposed to give inferior performance on ADSL, because the B10D lacks a filter present in the high quality analog front end of the B10A.
It is possible that a very good modem might give you more speed, but I do not imagine it will be a huge amount. Ask for modem recommendations from people here who know what they are talking about and are FTTC users if you wish.