Might I suggest that we start at The Queen"s Vaults. [Maps Link]
It"s pretty central and within easy reach of Central Cardiff.
If various people want to meet up at whatever hotels they are at (PI or TL) they an organise cabs separately etc.
Why The Queens Vaults? It"s OK but there are loads of better pubs in Cardiff. It is pretty cheap which is an advantage and also has a few pool tables and a Darts board, but we are not likely to be playing those during the meet up. It is not very big though and I am not a huge fan of the beer there.
The Great Western is the starting place imo. Obviously I will go with the flow though.
Also did you say you want to head over to the Bay in the afternoon. I will join you if that is the case. We can get a beer in The Packet, Terra Nova and The Wetherspoons over there (forgot what it is called). I assume most people are staying in the Bay area so will be around there at some point in the afternoon
