Something is wrong! When you say "charger" do you mean the on board charger in the car (unlikely), or the Delphi "granny" pEVSE? It is possible that you have got a very low voltage supply that is restricting the charge rate, particularly as you mentioned elsewhere that you are using an extension lead.The 8 hours is from fully empty so it should rarely take that long.
Being ignorant, but is there a facility on the granny charger to vary the charging rate? Normally they are restricted at 10 Amps but some can be turned down to 6 amps which would equate to around 1.4kW and hence around 12 hours.
Thanks for your post. It was whilst using the Granny and yes from empty. I have now managed to sort out a better 16amp connection from my garage after contacting an electrician, so hopefully things maybe swifter?