I'll have to apologize to both Reece and joedaman.
The motherboard Reece has is actually DDR4 supported and not DDR3.
I looked up the wrong motherboard. Sorry about that.
There are no mistakes only opinions which is what the OP asked for. In my opinion it is a huge faff to go around sourcing parts when he has £700 to play with.
His motherboard socket is 1151 - Already the latest Intel
His RAM is DDR4 - Already the latest version
If he buys a new motherboard he'll only be buying a board with DDR4 and an 1151 socket AGAIN in all probability. With no benefit. Complete waste of money.