Thought this might help others in the same boat. The software is very inexpensive and I use it all the time now.
Its a great bit of specialist Buy-to-Let invesment software that runs in your web browser that dynamically calculates the yield, gross return on capital employed, net return (incl. capital growth or without) for buy-to-let investment properties - its fantastic (oh and it's only £6.95 a complete bargain).
What I like is it really makes comparing Buy-to-Let deals across different price points very easy by boiling it all down to your return on investment. Also what I like is it enables you to adjust twenty+ financial variables to understand their effect on each invesment decision you make. All easily done through a user friendly graphical interface.
I can't recommend it highly enough, as I've been looking for exactly this bit of software for ages. But check it out for yourself at their website -
Buy-to-Let Investment Calculator - makedigital.com
I'd be very interested in other people recommendations and experiences. It seems a bit of a jungle out there and this kind of software isn't so easy to find.
Andrew.