To the OP. Collect your own seeds from everything. Plant your potato peelings, they grow too.

I recommend redcurrants, strawberries & brambles if you have the space. Cheap and abundant and plants last for years. I don't recommend throwing your strawb plants away and replacing them every 2 years. Mine are about 6 years old and yield huge crops.

Feeding does make a difference. e.g. I have a young pear tree, got half a dozen fruit each year till last year then I fed it just before flowering and I got pounds and pounds of fruit. HUNDREDS!

If you're going to have an apple tree I've read 1 cox's apple gives you more vitamin C than 2 pounds of golden delicious.

Tough polythene by the metre off ebay is cheap. You can build tunnels or geodesic domes or anything these days, on the cheap. You can buy hub connectors from ebay too.

Tyres, if you saw off an inch or two from the rim (both sides ) then turn the tyres inside out, they can stack as high as you like for a potato tower. (an inside out tyre has much more space inside than an ordinary tyre, and it stacks tightly)

Keep watching the local ads for cheap timber, railway sleepers, glass, polycarbonate sheets, pots, bricks, slabs, anything. Growing your own shouldn't cost a fortune. Shops like lidl, home bargains, etc, sell fruit trees, seeds etc cheap.

Get your chops around these

Just a reminder, when saving seeds and getting ready to germinate...many will need to be put in the freezer or very cold fridge for a few weeks. This simulates winter so the seeds thinks its spring and time to sprout when the temperature adjusts to the atmosphere when you take them out. The friend who gave me the strawberries stores all her seeds in the freezer, and swears they last for years until she is ready to plant them. Kind of a rotation alternating the variety since she has so many. Good Luck and post pics of your seedlings and tunnel. Would love to see it.

@Sunflowerstar and kawika

Thanks very much for the advice and links, I have never considered freezing seeds before, and I will definately check the books out tomorrow.
Cheers Guys

I started this thread last year when I was about to embark on a different style of living, trying to become a little more self sufficient where I can. I wanted to ressurect it again as now I feel a fair bit of progress has been made and hence I am keen again to soak up any advice you guys have.

I now have the polytunnel up and running, 28ft x 10ft
I also have a flock of 14 laying hens to boot

Am keen to take it a step further now, realising that if I in reality have a cap on my earnings, then the way forward is to try to save money and make what I do have go further. I love looking around sites which recycle and reuse "junk" such as pallets and again, would be appreciative of any handy tips of stuff you have tried out that work.
Cheers in advance