Newbie-

Hi and welcome. There are many varieties and suppliers of asparagus so your best option is to Google what are the best ones for flavour and suppliers, look at a few results, then choose the one that appears the most but don't opt for the cheapest supplier.
Having just had a look, there's asparagus lover.com, www.gardeningknowhow.com, Request Rejected › magazine › home-garden, asparagus (their recommended suppliers are Blackmoor Nurseries Fruit Trees And Soft Fruit Plants For Sale | Buy Plants Online and Pomona Fruits Fruit Trees For Sale UK & Soft Fruits | Pomona Fruits) and also FreshPlaza: Global Fresh Produce and Banana News. Our John on this forum has a book you can buy plus there's a growing guide at the top of the main page. Hope this helps.

I got my crowns from Pomona Fruits and was very pleased with them.
I bought 2 varieties, Mondeo and Guelph Millennium.  On my clay soil, which is not so well drained, I found the Guelph did better than the Mondeo.  They are in a raised bed which helps the drainage a bit.

Hello Newbie.  I live in north Essex and probably have the same soil as you do in Kent.  I grew my asparagus from seed three years ago and have 8 feet high plants currently.  We had an excellent crop this year (3rd year).  I dug a 3 metre long trench, two spades wide, one deep and poured 25kg of grit into the bottom which I then forked in about half the lengths of the tines.  So a total depth of about 2 feet.

One thing I have learned about asparagus is the amount of misleading and almost religious guff that is written about them.  "I get the asparagus pot boiling and then dash out into the garden to harvest the spears and dash indoors to plunge them into boiling water" The Telegraph  What tosh.  People buy asparagus in supermarkets that's grown in Chile for goodness sake.  The best advice (and this has been verified with many veg growers is to harvest anything about a span of your hand tall, but wider than your little finger, with secateurs, up to but not past the longest day.  That's it. 

My wife cooks them in home grown chopped and fried garlic with butter with a bit of olive oil in a griddle pan or frying pan (I am not allowed in the kitchen).  Cooked to slightly singed frond-end - delicious.

By the way, mine have even self seeded this year to the delight of friends and familly.