I take it that they are two separate £12.50 e/w Accas mate?
The return is impacted hugely by either all winning or 1 or more not winning as in the first example if all 4 win then your returns would be £7,312.50(win part of bet) + £197.26(Place part of bet), giving a total return of £7,509.76 BUT, if you had 3 winners and one 2nd for example then you only win the E/W(Place) part of the bet which is £197.26.
Of course you could get the nightmare scenario of getting 3 winners and one finishing 4th in which case you would get the square root of fekkk all.
Hope that helps mate.
Erm each one ive done on bet365 has total stake £25, EW £12.50, doubles my stake for each one i did for some reason.
thanks for the link Ace too.