If you're from the UK, no matter what speed you are going, you've gone onto her road. Speed is an entirely different kettle of fish; despite how unfair it may seem. There's a lot of UK driving laws which suck ass, and this being one of them. Another example is if somebody slams on their breaks and you fly into the back of them; you'd be liable for not staying a good distance away (unless of course you could prove they did it purposely). In this case you more than likely have no proof of their speed, and are only estimating yourself.
By the sounds of it, you're fucked.