Early blackbird eggs

Hi!

We live in London Zone 2 and were overjoyed last year to have a blackbird nest on our balcony. She had two sets of eggs and most of them hatched and survived.

We thought she wouldn't return but we found she has returned this year. She has already laid two eggs which seems very early. Are there any suggestions of how we can help if the weather turns cold? Any food that is good to leave out? We don't go out on the balcony when the birds are there to give them a bit of space. 

Thank you!