If you've not been running much, for any of the numerous reasons why running is put to one side, don't try to get up to the current week of training for Ealing Half in one week. In particular, if you've missed the first week, don't try to do all the runs for the first and second week in the second week.
Look at:
where you are (honestly),
how much increase in mileage your body can normally cope with (do you get injured easily, can you cope with distances up to 10k easily but need to build up after that?)
and design your training plan based on these.
Here's a useful article about increasing mileage