If approached as mine-to-play-with-when-I-want-at-zero-notice, then shared ownership won't work, but as a route to more affordable flying, it can.
The Kiwi syndicate works well - with 23 owners. Each share is about 3,500UKP or so, including an overhaul reserve. Insurance, doubtless far more than would be the case in the UK, works out at about 40UKP/month. Once you've flown 7 or 8 hours over a year, it's cheaper than local self fly hire. Not all the owners flew regularly - whilst I was there, the majority of the time was flown by five or six and availability wasn't a significant problem. Owners were PPL students, CPL students, hour builders and recreational pilots.
I guess a syndicate of around 12 or 15 could work well in the UK.