Thanks to all for the helpful responses so far - much appreciated
To answer a few questions, and to provide a bit of extra background, I would start by saying I'm based in the UK so that in itself seems to limit my options for hiring lenses or finding accessories at reasonable prices! I got the camera from a UK dealer for what I would consider a good price, but in the knowledge that this was in part due to the fact it's no longer repariable by Hasselblad if anything were to go wrong. I'm "only" an amateur so I won't be deriving my income from it...
It is the H3D-39 not the H3DII so I believe that means I can use a film back with it - is that correct? Not sure at this point if I want to bother with film but if the option's available it might be useful later.
It came with the 80mm lens and I expect to stick with just that for now. If I add anything, the suggestion of an extension tube and the 1.7x converter seems like a very good idea without layout down too much more money! Fortunately my wife is very understanding, but I don't want to push my luck
Previous digital gear has been mostly Canon, although recently I've "downsized" to Fuji X, and m4/3rds systems. Ironically I was finding the Canon 5Dii and a bag of lenses too heavy to lug around, but as long as I stick with only one lens this H3D will actually be lighter and smaller
With a bag full of lenses I often found I would gravitate towards a 50mm in 35mm terms, so the 80 on the Hasselblad should do fine.
The one accessory I do need soon is another battery. The camera came with one LiIon, which acccording to the paperwork appears to have been bought new at the beginning of 2014, so it should have plenty of life in it, but a backup is probably essential. Does anyone use the 3xCR123 battery grip as a backup? I assume that would be cheaper than a LiIon?
Anyway, enough rambling on. Sadly I can't use it during the day as work takes priority over my time, and it's dark by the time I get home so I probably won't get to play in earnest until the weekend. But it will go with me everywhere at that point so I can get to know it