It will be interesting to see how it pans out. The reason I suspect most people here are right with their pricing guesses (that the 5c will sit below the 5) is that current 5 owners would be rather frustrated if their device suddenly went from top of the range to bottom of the range overnight (unlike currently where it goes to the midrange slot).
My guesses
5S 32/64/128 £529/£599/£699 A7 LTE / Fingerprint / max ios 10 / sold for 2 years
5 16 £449 - As is / max ios 9 / 1 year left on sale (for 2 yrs total)
5c 8/16/32 £299 / £349 / £449 No LTE / No fingerprint / slower A6 / 1GB / max ios 9 / updated each year
My guesses
5S 32/64/128 £529/£599/£699 A7 LTE / Fingerprint / max ios 10 / sold for 2 years
5 16 £449 - As is / max ios 9 / 1 year left on sale (for 2 yrs total)
5c 8/16/32 £299 / £349 / £449 No LTE / No fingerprint / slower A6 / 1GB / max ios 9 / updated each year