We went for 300 to start and it was more than enough for two of us in the house - two concurrent VPNs running teams all day, Ultra HD TV streaming, many, many random work and personal mobile devices. All no problem at all.
However we did move to 500 a few months later, but that was not for the fibre speed. Rather because the Halo 3 deal was the cheapest way to get double mobile data (as we used to have pre-FTTP) plus the fallback mobile data options in the event of a fault (even though that is much less likely now with FTTP). £6 extra a month for 4GB extra on each of two phones whilst still keeping roaming and TNT sport (which you lose by going to EE). The extra 200Mbps on the broadband was only a bonus for us in this decision!
I can honestly say there is no practical difference - in fact despite the WiFi disks included in my deal most devices still only get 200-300Mbps around the house as they only get 5Ghz single band wifi. I do squeak 500Mbps on my desktop but only because it is wired into the back of a wifi disk so it gets to use both bands.
Actually there may have been one benefit - probably knocked some time off a download of Fallout 4 from Steam. But that really is it.
