Toffee - Here is how to Sonlight on the cheap!
Go to the website and request a catalogue (much easier to figure it all out with a paper catalogue and a 
Join the sonlight uk yahoo group.
Say you are intrested in using Sonlight but are worried about the cost, mention which cores you might be interested in - with luck someone might be about to sell what you want. Sometimes people sell a whole package, sometimes a few/lots of books, sometimes just an IG (instructors guide).
Once you have a catalogue its much easier to see what is what. It not longer includes a summary of each book, so you can find that out on their own website and reviews on amazon uk/com - whilst on Amazon uk you can find out how cheap each book might be available to buy.
Quite a few of the books you might not like/want anyway.
I have just ordered our first proper core (having just done bits from sonlight using their booklists before) and whilst it was a BIG amount of money, it isnt quite so scarey if I view it as a weekly payment.
If you are not a box ticker, you can Sonlight just using the book lists but having the IG as well is great if you like order and box ticking!
There are of course alternatives to Sonlight but its definitely what Im sticking with for quite a few years. Also bear in mind that its only really history, geography, bible, language arts and science (if you opt for science).
Also their curriculum presents a creation/evolution perspective (they are creationist but believe in presenting the alternative). From science H they use Apologia which is very creationist (as far as I can tell) hence we will not be doing that. Thats the reason why many Christians dont like it - because they want to present an exclusively Christian and creationist perspective.
There is actually an american yahoo group called "sonlight secular" which also might be worth a look.
Sorry for waffling on - I love sonlight and my waffling might help someone else too...............