I have used all these providers in their trial mode. Has anyone used them for real (ie afer paying the credit) and have there been any differences in quality? I mostly make UK landline calls so the call rates aren't going to affect my decision.....

I have used VoipCheap and am now using InternetCalls in 'paid' mode, they are all from the same company and call quality has been very good. I am using the latter with an incoming number (0121) and I particularly like the ability to forward calls when offline, away or unavailable, I forward them to my landline. Hope this helps.

Personally I'm using Voipstunt. Despite the fact that they are all branches off of the same fineara tree, voipstunt appear to have a greater selection of free countries. Look here for a comparison.
http://www.myvoipprovider.com/Free_VoIP/

Since paying my money, I've not noticed any improvement in quality. But then it has been good since the beginning. Occassionally you get an echo, or the effect of talking through a bucket of water, but just hang up and redial and it usually gets sorted.

Perhaps when I get a decent connection, I'm only on Telewest 10mb, then it might improve. Roll on the year when TW & NTL bring their 100mb service

a very nice man wrote on Mar 17^th, 2006 at 11:42am:

Perhaps when I get a decent connection, I'm only on Telewest 10mb

:-?

I'm on a 2Mb connection, share the broadband connection with two computers and have two internet phone lines.  All works fine from here! ;-)