I did not think to put in my postcode first time round (which is odd for me).
It turns out that searching 'XXXXXX forecast' (where XXXXXX is my postcode) returned a much different result than searching 'Durham forecast'. I must reserve my judgement on which is the more accurate temperature data... One must also bear-in-mind that the temperautre of the phone is likely to be a funcation of: the ambient temperature, the thermal mass of the house, local heating/wind/shielding effects, dissipation of heat across components.
Further experiment may include: Test with GSM disabled. Test with Bluetooth disabled.
Also, I think it would also be interesting to compare these results to a high-precision Mecury thermometer.