Britishers? And you complain about us using non-words!
Do Britishers really pronounce "temporally" and "temporarily" the exact same way?
Some do, yes.
And is there really such a word as "nackers", and if so, what does it mean?
Yup, it's venacular for testicles - although I believe it actually has a silent 'k', as in 'knackers'. You could also be refering to a 'knackers' yard' which is a place old horses would be 'retired' to (i.e. sent off to be processed into glue and other horse derivatives). Knackered on the other hand originally meant 'sexually tired' but has changed into a more general meaning of 'tired'.
That help?