Basic core/strength exercises

[PhoebeMcPeePee]

I'm getting back into exercise after a 5 year break. I'm going out on my bike 2-3 times a week but only managing 20/30 minutes at the moment as I'm so unfit . I'd like to add a short routine of strength / core exercises I can do when I get back from my ride & wondering what is best to get me started. I'm thinking 3 sets of 8 lunges, squats, push-ups (on knees at the moment!) crunches & a 10 second plank then a good stretch to finish. Anything else I should add other than some hand weights as I progress.

I'm still losing weight (1.5st gone same to go) but ultimately just want to be fit & lean again

That sounds good, all those body weight exercises should strengthen you up pretty quickly. Oh, side plank too maybe?

Here are 2 more I took away from a core & abs session:

Lie on your back with your legs pointing straight up. Try and touch your toes!
Lie on your back with your hands under the small of your back. Put your legs straight up, then lower them (together) while forcing the small of your back to the floor. When the small of your back comes off your hands, raise your legs.

The basic core strength exercises are Plank, Push up Plank, V-sit Hold, Twisting Crunch, Stiff Legged V Bend, Lying Windmiss, Plank on a Swiss Ball, etc.
These exercise will strengthen your core muscles.