Like Mark I can only comment on the Falke really. Without a hard to replace rear sight and front sight blade its value is diminished, so I'd say under £200 too. Not sure about the BSF but I did read the other day that front sight parts are in stock at Chambers. Value probably a bit less than the Falke, I guess. Pics would help.
Edit: for anyone that buys the Falke and wants to fabricate a front sight element - which is highly profiled but nevertheless a single piece of metal - I can help with dimensions, pics etc.