Exclamation OTA Update of GPE 4.4.2 to 4.4.3 causing major issues

Hi all,

I installed an update today for 4.4.3, clearly i shouldn't have as its rendered the phone almost useless. Screen isn't displaying things properly, i can't really describe it, but have the pixels are missing intermittently. Also there is no poweroff dialogue and hardly any apps load.

Why isn't it possible to use the OTA updates, and what's my resolution now?