alternative to soft play blocks

[lirael]

I wondered if anyone on here would have any bright ideas? I want to construct some sort of indoor obstacle course for Ds2 (10). We have a soft play trampoline but I want something he can balance and climb on. Soft play blocks are prohibitively expensive. I thought of making a balance beam with a plank of wood, but can anyone think of a cheaper alternative to the blocks? I have about £150 to spend, as he's just had a birthday and everyone always gives money as he doesn't really do presents.
TIA oh wise Mnetters - though I am probably a bit daft posting this at this time of night as it'll have disappeared by the morning...

cushions from a charity shop? or freecycle sofas? or just freecycle?

Foam cut to size foam

Ideas for an indoor obstacle course

We made wedges etc with foam given free from a furniture upholsterer or for just pence. They had skip loads of left over foam chunks and sheets of foam, so try there. Covered in lovely coloured end rolls do material makes lovely things. Maybe simple MDF squares covered with foam?

I use masking tape/duct tape in diffferent colours to mark off squares and balance lines for hopping/tightrope walking.
I have marked out a figure-of-8 with tape and using floor tiles.
These are nice prone activities.
I have this in my hall which goes in and out of favour.
What about a body sox? Or a wobble board?

Great ideas everyone - thanks. Have bookmarked and will look properly later. Like the idea of using foam shapes - that site looks brilliant Dev9. DS doesn't follow instructions very well, so all exercises have to be simple and obvious. He's also very cautious, so won't balance on anything that isn't firm - one of the things I want to work on.