[Leica] Need help pricing sale of photograph

[mail at steveunsworth.co.uk (Steve Unsworth)]

Can anyone help me? I've been approached by someone wanting to buy one
of my photographs for use in a newspaper advertising campaign by a
travel company.

The problem is I don't have a clue of what to ask for the image. They
want to either buy the photograph outright for multiple future use
(which I'm not very happy about doing), or buy it for a single usage in
the campaign.

Can anyone give me an idea of how to price this in the UK. I expect the
final price will depend on whether it's a national campaign, or just in
the local press, so I'd really appreciate some kind of ball park figure
to go back with.

Thanks in advance.

Steve