Hi Stu,
Not exactly what your requirements are (volume, speed, budget etc), but
Scott on this forum does large format printing. I know A2 isn't exactly massive, but I've used him in the past to do some posters for me in the past. As you know I'm pretty particular and he worked with me to get the right results. Only downside is if you need it immediately it's not possible. But he generally gets it to the post office and you'll usually have it to the next day.