Looks like SF are selling the same Bosch set with a 3rd battery for £189.99, so you are paying £40 for an addition battery. I am always a bit weary at buying this time of year as there may be something available in the next new year?, but having said that the OP did mention that this set was advertised at £180, so a reduction of £30. Nevertheless a good deal for an impact and driver set. A 3rd battery would be ideal, but something like a 2AH would be more ample when doing larger jobs.
or this one £120 with 3 batteries http://www.screwfix.com/p/dewalt-dcd776c3-18v-1-3ah-li-ion-cordless-combi-drill-xr/13165 Just too many choices. They will all do the job you need
Would agree with above comment about the Metabo LiHD batteries - absolute belters, honestly. Not bad price either - http://www.snapco.org/product/metabo_18_v_lihd_3_1ah_battery Had no bother with them so far, would recommend them. Not too sure about Bosch unfortunately!