Tips for eating cheaply in London?

[JacknDiane]

We are visiting next month and im looking for ways to eat within a tight budget. Just dh one dc (teenager) and myself. No allergies or particular needs. Love pub grub and Italian. Would like a sit in meal at night.
We haven't got a particular agenda, just planning on going with the flow.
Any ideas appreciated. We are in a hotel without breakfast so can't sneak the croissants!

That menu looks fab for the ymca!

Thanks so much to everyone here for all the great advice.

Thanks. I hope you have a wonderful time, @JacknDiane . It's great to when you think the OP is nice.

Which area is your hotel in - as people may be able to recommend good pubs for food nearby for the evenings? Most of the pubs in very central are poor but there are a few good gems.