Good third party routers are Asus, Billion, DrayTek, FritzBox and TP-Link.
The model you decide on will depend on your requirements and budget. DrayTek and FritzBox are the most expensive, you won't get a Fritz sub £120 and DrayTek are even more expensive. TP-Link had some issues with IPv6 earlier and have had almost a year to sort it out, so check before buying. The others all have full IPv6 support out of the box. Whatever you decide on get one that supports VDSL.
Avoid Netgear and Linksys if you want IPv6, they don't support it properly.
Just to add to Liam_ comment about TP-Link.
There is a beta firmware that you can get from TP-Link support that works ok.
My only concern is about any future 'released' firmware and backwards compatibility.
Having said that the TP-Link VR900 V2 I have has not had a firmware update for over a year, probably proven itself with the V1