Thank you all for your thoughts on this.
I know the shop and the area quite well as a regular customer. Couldn't be a more perfect location and while there is some marginal local overlap there isn't any direct competition for a long way in all directions.
The reason for selling is genuine, as far as I can see, not a failure of the shop or lack of customers but more about personal burnout. The owner is a young woman running the shop all on her own. I had a chat with her today and I can really empathise with her burnt out feeling as I feel the very much the same in my current line of work. I desperately need a change as much as she does.
Her lack of motivation has held her back in developing the shop in a number of very obvious ways to me, which she is aware of and we discussed. Just how I feel in developing my current business further - I have been wanting to get out for a very long time but just couldn't see the way.

If the numbers add up this could really be an opportunity, but only if the numbers add up, as our life here relies on my income entirely.
The owner will let me have a copy of recent accounts tomorrow so I can have a more realistic view of the figures involved and any further steps depend on that really.