Hi ya, I am new to all this as well, from what i can make out it all depends a little on your own circumstances, if you have the indoor space you can start some seeds off in seed trays in the airing cupboard. Or if you have a sunny window sil that doesnt get too cold.
I have just germinated a load of salad leaves this way and will be hoping they make the transition from airing cupboard to window sill without all dying off.
For outside on your allotment I think the emphasis is on getting the ground ready. There are a few things you can plant if you cover them over with a fleece, but personally and i say this with no expertise, but i’m expecting there to be the big cold icy patch, the ‘winter’ if you like that seems to have slipped a season and hits more in Feb March time in recent years. So i would be a bit dubious.
Again there are things like fleeces, cold frames etc which all add to the initial layout. Although with some internet searching you can find some great DIY options too.
Still what do you want to grow? do you want to stick to the food that you actually eat? are you wanting to try and be a bit clever about it so ignore carrots and potatoes as they are cheap to buy and try and grow the more expensive stuff? or are you wanting to grow some really random stuff in order to try out new things, like the purple carrots etc.
I think the best advice is to try and start off simple, get into the routine of it all, if to make it too big an effort or hassle so it becomes a negative chore the fun and enjoyment goes along with the interest and you risk giving it all up before you really get going.
if you go round the charity shops, their book section is usually full of gardening books which has all the information, veg/herb at a time when to plant, when to harvest as well as information on pest control and pretty much all you need in one or two books for anything from 50p to maybe a couple of pound each.
Worth looking at.
Anyways i have rabbited on in circles without really answering your questions, but you need to try and refine it a little to what you want to grow what you want to do. Then can look if its the right time for the foods specifically you are wanting to plant.