Your £2 gets you free downloads for a month, you can pay an annual subscription of £20 which is much cheaper than similar products etc charge for access to their database.
Also, they offer an incentive program, if you are the first person to spot a new static speed camera location that gets verified you earn yourself free membership for life.
If you read the T's & C's the £2 is for membership of the site, the database is a free benefit of membership (otherwise they could be stuffed under the SOGs act for selling something that was not up to date).