Thanks for the benefit of your wisdom folks, appreciate it. I'd pretty much come to the same conclusion and won't be pursuing. What a mine field this hobby appears to be! I'm musically 'keen', play some other instruments and would love to take up the concertina but put off by all the comments about cheap Chinese models with no longevity, or hit and miss quality. It leaves me with the impression that most of the new sub £1k concertinas are all flavours of the same standard components re-badged to fit a particular price point. How on earth does a novice choose what a 'good' investment is and at what price point an appropriate level of quality kicks in?
The only reason I was looking at vintage was because of the recommendations of others on various forums but I guess it needs to be a guaranteed, renovated vintage model which probably equates to far too much money for someone wanting to dip a toe.