Thinking of buying Flat Mobile Joomla! but...

I've installed the free version on my site www.westcountrylets.co.uk and it seems to work (got through to Paypal payments screen on iphone) but looks absolutely terrible.

If I pay for Flat Mobile Joomla will I be able to configure things like the width of the forms for name & address details? (as well as adding logos etc.

It depends on the form you use, usually it's possible to fix CSS in template's custom.css file, but sometimes forms are displayed as iframe and don't fit mobile screen width.

Try to adjust styles in current mobile template to check that it is possible.