Hi,
It's a bit of a nightmare upgrading to 312mm with the 110 TDI, because you have to upgrade the hubs and calipers as well as the carriers, discs and pads, because the carrier on the 110 TDI is attached to the hub.
So you're looking at a fair bit for the whole lot, many hundreds of pounds, so the first thing I recommend do is upgrade the front pads like I did, as that will make a huge difference.
The ones you want are Ferodo DS Performance FDS1398, which although are £100, they give great stopping power and are much better than standard, so I think you'd be fine with them.
It's also important to bed new pads in properly, and you can find guides on doing it - I got mine hot, smoking and stinking & afterwards they became much better.
Btw, the Ferodo FDS1398 pads are better than Green Stuff, etc (I would stay away from EBC stuff for sure), and would easily be enough just for a Stage 1 remap (like I've got as well)
If you need new discs just get standard OEM quality ones (the more expensive ones on Euro Car Parts), not cheapo EBC 'turbo grooved' or any nonsense like that, as they're generally crap quality and can break.
-You don't need grooves with a remapped 110 TDI, and even if you wanted them for looks, you can get eliptical grooved discs from Badger5 here on SCN, which are much better than EBC grooved/drilled discs.
The eliptical grooves look the best and give the best performance, but they add cost, and you don't need them unless you're racing on a track, in which case the extra heat dissipation would be good in helping to avoid the discs overheating and the pads fading.