I've been watching this TV for a while now. With the 5% voucher (YAW744) it takes the TV to £664.05, which is the best price I've seen. There are other vouchers listed here at HUKD but they seem to have expired. Then there is quidco @ 3.5% which is £23.24 so a price of £640.31 after quidco.
It's a very nice TV for this price range.
Alternatively you could try to see if John Lewis will price match this £699.99 with the LE40M87BD* as it is also a high street deal (it's advertised as a March deal in store). This way you get JL's 5 year guarantee.
* It's the same as the posted model but has a silver strip, instead of black, at the bottom. It also looks better IMO. The M86 is exclusive to currys but aside from the colour change its identical.