Pengwyn, I wouldn't rule out the N95 although Herbie is right the accuracy is only about 10 metres, you can buy a good bluetooth GPS for about £20. You will need a good phone to run the software on therefore the N95 is your friend.
Currently the battery life would be a problem to play a full round of golf using the GPS on any of the GPS enabled phones, I don't think you would be able to complete a full round. Once again if you went for the bluetooth option this would not be so much of an issue.
Unfortunately I cannot vouch for any of the software available as I have not tried any of it, although this is one option I am considering for GPS golf as I already have the N95