Tesco currently has offer of free delivery on electrical spend over £50.
However, the free delivery kicks in when buying a £9.97 cordless mouse http://direct.tesco.com/q/R.207-3695.aspx
You can then return it to store at your convenience within the 28 days.
This is handy for those of us who don't have an order/collect store or who don't want to pay the £5 P&P.
EDIT - just realised this is apparently a very good price for this mouse so you may not want to return it afterall!!
Have posted mouse deal separately.