Although being wooed by Carphone Warehouse, I eventually went to Phones 4u, where there's an excellent branch in Plymouth, just down from the shopping mall, and where I got a fantastic deal which saw me virtually not having to pay much more a month than I was before, but now enjoying everything the BlackBerry has to offer. I can't recommend Phones 4u too highly!
One consequence of basically continuing my previous contract, was that I retained a limited SMS account, but never going over 300 a month, this was no hardship!
However, on my previous phone, there was a built-in SMS counter, but strangely on the BlackBerry there wasn't one.
But with all the apps now available, I found a 'SMS Counter' which cost just a couple of pounds, and which does the trick.
The only problem is that it doesn't appear exactly as it is advertised, and a couple of its features are not overly clear. As with most things, there is a support service to email, which I have done now, more than once, but with no response. It's not crucial to me, but I've noticed other occasional references to this particular company NOT bothering to reply.
So, just in case you're considering an app from them, bear in mind that their promised support might not materialise.
The company is called GetEmpower - you have been warned!