Reliant Parts World will supply a reconditioned 850 engine for £975 excluding VAT and carriage if thats any help to you.
There must be a market if they are offering them I would have thought. My own experience of things tends to show a lot of people want something for nothing. If you have been doing this with 2CV's though you will have a lot more idea than my own personal dealings.
Not sure from your posts what the finished price would be though sorry Al