Private Dentistry, Invisalign experiences?

The missus broke her front tooth recently and found a well reviewed private dentist to fix it. I went along to the consultation with her today which was really eye opening vs the normal 'NHS + some private work' place we've used up until now. The dentist was excellent, and spent nearly an hour examining, taking photos and x-rays, then walking her through the various issues and possible treatments. He was verrry good (the 911 GTS in the car park obviously doesn't pay for itself ;-) )

She asked about getting some teeth straightened and he suggested Invisalign. The cost is one thing (about £4k) but I also hadn't realised that as well as 9-12mths of wearing the moulds for 20hrs a day you also then have to wear them at night, effectively for life in order for the teeth to maintain position. He also suggested having wire retainer fitted. To me this all sounds like a massive ballache - was wondering what other people's experiences were and whether they would recommend it?