Collecting seeds from vegetables Please can you tell me if I can collect seeds from a various number of vegetable plants for use next season?

if you are growing any F1 or even F2 hybrids any seed you do collect may/will not come true. a carrot will still be a carrot but may not have the flavour/size/shape etc. But for carrots/parsnips etc the plant will have to remain in the ground and they flower the next year as they are biennials. so an area of your plot wont be productive next year as you are growing the plants for seed. if you have any seed left over this year keep that sealed and in a cool dark place and then you could use that next year.
certainly runner/broad beans are fine and I always seem to find a couple of pods that just didnt get picked hanging on in there in the autumn.

I grow all female cucumber plants and cant sayI have noticed any seed in them.

I have tried to harvest toms with no great success.

i do find cherry toms and shirley do ok for seed.

Pumkin, broad bean, are two i have in now from last years seeds and both are growing well.

1 gardeners delight tomato has enough seeds for anyone, I just wash the seeds and leave them on a tissue to dry, even for a few weeks, stored till the next year and they are fine, I wouldn't risk any other veg, I buy seed online, much better value.

Thank you all for taking the time you answer. Some great advice once again.