Thanks for all the replies. I do assume that leaving the EU does not mean that the UK must withdraw from the jurisdiction from the UK - after all, the ECHR is governed by the Council of Europe.
I'm aware that a member state should ratify the convention; however, the UK as a state already ascribed to the EU before the pre-condition arose, must be exempt on the basis that they are not a new member.
The problem is there is so much uncertainty and so little (from my research) cogent literature which states what will happen to the ECHR should the UK opt to leave the EU (of course, this in determining the interrelationship I think this is a key point - though they are not mutually exclusive as you point out).