It is interesting to note that, amongst others, the rate for calling their 0844 numbers used by many GPs are increasing (from 1 Jan 2013):

Services g6 rate; from 5.11p per minute to 6.62p per minute

Services g11 rate: from 6p per minute to 6.64p per minute

Most Surgery Line numbers are Talk Talk type g6. Those added since the "ban" are Talk Talk type g11.

With the increase to the standard call connection fee, from 13.1p to 13.87p, the cost of 5-minute calls is increasing as follows:

g6: from 39p to 47p (20%)
g11: from 44p to 48p (9%)

Although the total package costs are increasing, the differential of £1.10 per month between Talk UK Anytime and Talk UK Evenings and Weekends remains. This is slightly less than the cost of 2 5-minute calls to geographic numbers (56p each) at the increased "penalty charge" incurred for out of plan daytime calls to otherwise inclusive geographic numbers - 8.41p per minute.

As ever, this begs the question of who would make daytime calls through Talk Talk, but expect to make less than 2 5-minute such calls per month. The 47p/48p has to be compared with zero, not 56p.