You can get a £10 M&S voucher for £5 at Bespoke Offers at the moment.
To get the voucher all you have to do is buy it for £5 at the deal link above, once you have done that you'll receive a confirmation email with the voucher attached and the voucher will also be available in the 'My vouchers section' of your account on the Bespoke Offers website. The voucher contains a unique URL simply click on it to access your M&S e-gift card. You can use the voucher online or instore, to use it online simply enter the voucher code at the payment stage or to use the voucher instore simply print the voucher and present it at the till so the barcode can be scanned.
This offer ends midnight 11/12/13 and is limited to 1 voucher per person, the voucher is valid valid for 24 months from 27 November 2013 or your last transaction.