Hello Mark, Can I ask have you heard of/tried any of the Adit software? They have some good handheld programs for both species recording (links into Recorder dictionaries, individual table and Location table) and habitat recording (creating a polygon for the GIS as you walk around).
I work at RECORD the LRC for Cheshire (VC58 plus Halton and Warrington above the Mersey) and we have used the Adit software on a number of occaisions and found it very useful, although I would suggest a PDA with a reasonably large screen 3.4", if you can get it, otherwise things get a little fiddly (to my mind anyway), but this would be the case with any handheld recording software.
We are just about to get some more handhelds for training purposes so we'll be looking to get a few new copies of the Adit software as well as the WilkKnowledge software (great pictorial keys).
http://www.aditsite.co.uk/index.htm
http://www.wildknowledge.co.uk
I hope they are as useful to you as they are to us.
Cheers,
Eric
Eric Fletcher
RECORD Manager
http:/www.record-lrc.co.uk