What job would you do?

Howdy, I have a dilemma. I work mon to fri in an office job, doing Admin 50hours a week. Pay is ok. But in order to be comfortable I also work sat and sun for an extra little in a shop. Here's the thing:

I am 54 I have to retire at my admin job by 62. But the retail/shop work they retire people at 65. I need to work until 65 as I have rent to pay, no partner and no family and no support. So I need to work till my very last day.

I have been offered a full time job at the shop (yesterday) , I will be £300 short a month as I will be working only one job and lower.

I could manage on less money by cutting but it's a big change. And a long term move.

What would you do.?

Sensible answers please.