Fucking Knob Head
Literally it translates as ‘fornicating penis head’, which bears no meaning, and therefore should not be used in the context of its literal definition.
Figuratively ‘Knob Head’ <noun> is an offensive British slang term used as a variant of "Dick Head" to describe a rude, selfish, dishonest, stuck up, mean, highly ignorant, obnoxious person or someone who has acted in a peculiar and/or ludicrous manner.
The 'Fucking' is used to add emphasis to the latter part of the phrase to accentuate the meaning giving more power to the user and further humiliating the recipient.
Jenny stop being such a FKH