Some seeds require light to germinate.... and some do not.

They typically need more light than a window sill can provide.

I do mine under lights. I also have a plastic cover that came with the flats to keep a "greenhouse" environment. I remove this when the seeds are up strongly. You can also use a clear plastic bag over them if you don't have a hot house type.

There are special mediums now available for seeds. These deter mold and fungus that typically kill germinating seeds.

The new guidelines for seeds suggest watering from below to avoid rot damage too. I've been doing this for 2 seasons now, and it works well. You just need another flat with no holes punched in to fill with the water. Put the cells in that for 15 minutes or so. and then back under the lights.

Some seeds need warmth to get going. Then once up, a cooler environment. Some seeds are really tricky. But most vegetables seeds are straightforward.

Park Seed has a nice catalog and a book on germination techniques you can buy. I just did a 1/2 flat of gloriosa daisies for next season this summer. Because I did not have my lights, and because it was cool they took 2 wks to come up. In my home they take about 5 days.

The concept is sort of like baking. Each thing requires a little special attention because of its needs.

Example for lettuce:
http://gardenofeaden.blogspot.com/20...from-seed.html

Tomatoes:
http://www.reneesgarden.com/articles...from-seed.html

If you got no germination at all? 1) seeds were not viable, 2) they got too wet or dried out once--it only takes one drying period to stop the germination process, or 3) temps were not correct for that seed.

I had 5 failures this past season, and the rest were successful. I expect failures every time I do germinate, in fact.

Using the special compost made for seed starting is very important. I mix mine with water in a large storage tub with a lid because I do this indoors and have to use my kitchen. This keeps the mess down. I wet the medium and let it sit over night till it is moist but not soggy. Sometimes I add extra fine vermiculite which I buy extra to provide more air in the mix.
Seeds don't like soggy conditions. Some of our nurseries have sales, so I buy ahead at lower prices for the next season.

I have found Park Seed to be a good resource for seed starting:
http://parkseed.com/default.aspx
Thompson & Morgan I think ship to all of UK. Not sure about Park's.

Here is a photo of my set up: I have a small table top light and this work type one in my studio. If you work in a basement where it is cool, you might need a warmth mat for warm requiring types of seed. You'll notice how close to the lamps the seeds have to be....they need alot of light so I raise them up as close as possible. This photo is showing 3 types of black eyed susans and some ornamental grasses.