Similar to Taffysblog, I too followed the instructions to replace the DPF additive on my 10 plate Cooper Clubman. Here's a list of my experiences:
1. Don't let anyone tell you the additive you buy off ebay is wrong. It isn't. The filling adaptors with the bottle (don't just buy the additive, get the filler kit too) fit the Mini exactly.
2. The biggest pain I found was finding a jacking point for a 2 ton hydraulic that gave you enough space to drop the jacking points onto a pair of axle stands at the rear. Get a piece of wood around 20-30cm long and put it in line with the plastic-covered sill just forward of the jacking points. You won't break the plastic as the load will be spread evenly.
3. The electrical connector came off in seconds; I couldn't get the fuel line connector off at all. Luckily you can drop the case and undo it under the car without having to take this off. Be careful not to pull on it or put any extra strain though.
4. Be prepared to saw through the bolt just like Adioz did. It is an absolute pain and you have to loosen the bolt just enough to get a hacksaw between the plastic mounting lug and the top of the case, but a bit of jiggling will give you the gap you need. You'll probably have to drill through what's left of the bolt into the mounting but a good-sized replacement bolt with two big washers will do the trick nicely. Frankly, I can't see how they'd do anything other than that at a garage anyway.
5. Regardless of what some people have said, you CAN reset the DPF through the trip computer. Do what Taffysblog says. It took me three minutes and is now reset to 80K.
Do NOT attempt this without a good jack and axle stands. Ramps would be even better, a pit or platform a gift from heaven. As most of my plastic undertrays had gone (other than the one over the DPF tank) the underside was absolutely filthy (duh) so wear protective goggles.
Hope this helps