2001 renault megane help please!!

Hi there



I'm new to this forum.. last year I brought a 2001 renault megane coupe 16 v 1.6ltr

it's been going great but I have been on holI day for a month and returned to a flat battery.. I thought I'd just buy a new battery as I wasn't sure what condition the old one was in.

I replaced the battery and now the car will not start. It turns over but no go.. it dose have a immobiliser and the key is not unlocking the car when I press the button now as it was before.

So I'm not sure if is a mechanical or electrical problem.

I'm also struggling to fund the fuel pump (first petrol car I have owned) thought I might be able to manually pump the fuel up.

I have also trird some WD 40 sprayed into the air intake but no go.. no difference.



Any help or ideas would be much appreciated



Thank you



Will