Help! Lightweight, cheap, can fit buggy board. What should I buy?

[HumpHumpWhale]

I have a 10 month old and a 3.5 year old. They'll both be starting nursery soon and it's a 20 minute walk. I need something that I won't break my back lugging up and down the 6 steps to my flat (possibly with 10kg of sleeping DD in it); that DS can stand on a buggy board because a 20 minute walk could take 3 hours otherwise; & that reclines so DD can nap in it on my non-working days. And budget is limited. Ideally around the £100 mark - or less.
Advice gratefully received!

Anyone?

I have a Maclaren Quest which I use with the buggy board and have since DS2 was about 9 months old. It can lie flat and isn't too heavy - I've had it 3 years now and it's still going strong!

Just had a quick look and seems like they're about £200 So over budget but a couple of friends have got lovely ones in good condition second hand from local FB groups or gumtree recently so it might be worth a look?

Ive got a mclaren xt that I regularly bump up to our top floor flat with a chunky 15 month old in. I'm also 8 months pregnant but it still doesn't feel hard. Most buggies could handle 6 steps I should think!

I'd go for something second hand. Our mclaren was very cheap and is used but absaloutly fine. A baby jogger city mini?