You have given yourself a stack of challenges there. Not sure where to start. Do you have any way of growing seeds indoors? Propagator? Seed trays with domes? Modules? You have quite a mix of stuff there most of which are not hardy and need to be started inside in the UK. Many should have been started with heat last month. You also have a LOT of seeds so you'll require quite a bit of space plus potting compost and seed trays or modules to get started. Only the sunflowers and sweet peas can be direct sown in the ground and even they will quite likely be mown down by slugs or snails if you don't watch carefully. It is still too early for the sunflowers but you could try the sweet peas. However, they are better started indoors and then planted out. I sowed mine in January and they were planted out three weeks ago. For the rest it is already a bit late to get flowering size plants but no harm in trying.

I think your best bet is to actually Google each species because I can't give blanket guidance for so many different things.

Also we need to know if your tomatoes are indoor or outdoor types. If outdoor you still have plenty of time to sow them. If indoor sow them asap.

As well as Googling, each packet should have clear instructions on it. Just follow them. However, your list is quite a tall order for a beginner. You have picked a rather complicated set of seeds to start with.

I am wondering from your vocabulary if you are an American living in the UK?

As Corp.Jones would say "Don't Panic!". Many gardeners in UK recommend late sowing as you get fewer losses from damping off.I'm going to suggest you use a cold frame, however. Site it next to the house where you get night warmth from the brick.If you need advice on this I'm sure there is a FAQ.

Cosmos - needs warmth but is fast. Sow direct mid June to flower August- October. Save the seeds and next year start them about now. Can't be planted out till June anyway.
Pansies - sow in modules in cold frame ideally from March but not too late now.Hardy so will flower until winter.
Sunflowers - likewise but less hardy. Don't sow direct.
Swan River Daisy - best sown early in warmth in sandy modules with good light. Wait until next year.
Johnny Jump Up - Viola? Pansy ?? If you have light soil you could try a few direct in mid May for late flowering. Surface sow and cover with sand.
Geranium - I'm not a fan of geranium from seed as it is slow and needs both warmth and light. You won't get any to flower this year whatever you do. Buy a few plants - it's not a lot more expensive than from seed anyway and cuttings are so much easier.
Cherry Tom - sow now in cold frame, plant next to a S wall if possible.
Lobelia - tough from seed. Buy a few plants.Is getting hardier in UK with GW though. Can self seed even. Don't ask me why it will do this, but damps off so easily. Leave the dying plants on a sunny, mossy wall!
Snapdragon: Sow in sandy modules in the cold frame, plant out as soon as risk of frost is past. Save the seed.Can be hardy so sow a few late (mid June) to flower next year.
Tagete: sow direct, late (mid june) in a hot dry spot. Save the seed. Will flower Aug - frost.
Anagallis: never tried this but it's a very delicate plant, so probably best first in the cold frame.

Final word: There is a saying in N England, "Ne'er cast a clout till May be out" ie. "Don't plant out tender plants until June." On the positive side with GW fall has been getting milder and frosts are not coming until late, some years not until November, so late sowings can often give an excellent autumnal display. Good luck - Ian.
PS: Where in NW ENgland?

It's okay! I'm actually wishing I had more time so I can try more seeds myself; I'm still learning when is enough water between two brands of seed-starting foam-type kits!

The link below is something I use as a guide to how long things will take things to germinate. If it's too late, see if the seeds will last until next year.

For propagation, look for the best places to get heating pads, soil and/or kits, and lights. These things will be able to be reused, so if you start slow and shop around, you won't put too much strain on your budget, and you can maybe take advantage of sales over the winter months.

Creativity can be a boon too- anything can hold soil, after all, and I've seen people use things like plastic milk jugs or cup halves.

I can attest to cosmos being fast growers! If the weather is nice and sunny, you can take your flats out during the day too to get a nice boost of sunlight once they're in the seedling stage.

Here is a link that might be useful: Germination info

I have limited indoor space for seed starting, so I often don't start my perennial flower seeds until I begin hardening off my pepper and tomatoes. It may not be ideal, but our summers are lasting a little longer, and our falls are more mild, so by the time I get them planted out in late June, early July, they seem to do fine. I really couldn't do it if I had to try and start them all at once. So, you might say that I am chronically/intentionally late with most of my flower seeds.