Great British Escapades: Inept Gardeners Question Time

Rightyho, you may remember that last autumn we created ourselves a vegetable patch, well the time has come to plant it so today I trotted off to the very lovely little garden centre in the middle of Grange-over-Sands and bought myself some stuff to plant. On the advice of the lovely lady serving me I opted for some seed potatoes (Maris Piper), some seed onions (just looked like very small onions), a packet of carrot seeds and a packet of spring onion seeds (it's only a tiny plot at the moment).

Pint sized veg plot.

All items have now been planted but, as I planted them, a few extra questions occurred to me which I hadn't thought to ask at the garden centre and I was wondering if any of you lovely folks could help.

As we dug through the home made compost we discovered a sprouting parsnip top so we planted it. What are the chances of it growing?
Does 1 seed = 1 carrot?
Why do I have "seed potatoes" but not "seed carrots" - aren't they all root vegetables?
Does 1 seed potato = 1 potato? (I hope not, seems a bit silly if it does!)
How will I know when they're done?
What pests do I need to watch for?
Do I need to do anything else now other than make sure they're watered?
Will the fact that the Morecambe Bay silts underlie the whole plot affect the growth of the plants? (that's why it's a raised bed - our garden used to be tidal 100 or so years ago).
Will they really taste better than shop bought?
Why is it called the "simple life" when it requires so much effort?

I appreciate these are probably very silly questions, but I'm a novice here and what I lack in knowledge I make up for with enthusiasm! Many thanks in advance for any and all help.

You may be wondering where my adorable husband was whilst I was busy with the planting, well he was getting up close and personal with the local wildlife and got these rather lovely pics. I say "lovely pics" but if any of those critters start eating my seeds, there'll be trouble!