Not really sure Stoner – most of what I do is with wood anyway, so I'm not entirely sure. I bought a set of Bosch SDS bits with the drill when I got it and IIRC, I've only ever used the 6mm bit (for big skirting into brick/stone/concrete) and one of the chisel bits for chasing out some plaster for sockets at home (something I wouldn't dare do in a client's house – not really in my skill set 😉 ).
SDS bits are way way cheaper than they were a few years ago though. I'd say get mid range 5mm (red plug, for No. 8/10 screws), 6mm (brown plug, for No 10/12) and a couple of chisel bits. The beauty of SDS is that it doesn't put too much pressure on the bits so unless you're using some £500 million volt cordless jobbie day in day out, you shouldn't need anything too pricey. Think it's best to buy the bits as you need them. Kinda like bike tools I think – better to buy one at a time and decent rather than a set and find there are ones that never get used.
The one "premium" manufacturer who's bits have always let me down is DeWalt (their screwdriver bits chiefly) and also, avoid Erbauer – both appear to have been made from cheese. I've never bought anything "made" by Bosch that's let me down.