I don't understand that at all - I am on page 1 of Google for the keyword 'treat colic', so something is working - just not how I need it to!
Here's my summary of what has been said:
Being #1 is moot in terms of sales unless people are
A) searching for that term / finding reference to your site
B) clicking through to your site
C) clicking on your sales page link and
D) feeling the pain strongly enough, trusting you enough, and believing in your solution enough to pay the 5 quid.
Do you know the numbers of people you've got at each step and where you're losing folks?
Google Analytics will tell you how many, where from, and how long people visit your site. If 2 people per day visit and immediately leave you can guess where the problem lies.
Possible solutions depending on where the breakdown is:
A)
http://screencast.com/t/MzU4ZDk2YTg shows 7 searches a day -- you can't get more people to search "treat colic", but you could add more keywords you show up for or you take the second half of the above and promote your site on more places than just Google.
http://screencast.com/t/NmRiM2Q5Z <-- Looking at treatcolic.co.uk versus the .com: they have 23 pages indexed -- you've got 20, they've got about 10 backlinks -- you've got 1300, they've got 2 of the on page factors optimized -- you've got all 4, they've got PR5 -- but you've only got PR0. They are obviously doing something right in google's eyes that you aren't. Some of that may be that they are a 4 year old domain and yours is from Jan 2010, but I'd go study their site through google's eyes and keep that in mind when updating yours.
B)
http://screencast.com/t/NDFkYWM3 shows the lack of a call to action in your meta-description. Compare it to the other sites on the screen.
C) There are an awful lot of blinking, bouncing, distracting items on your front page. If I'm sleep deprived because of a colicky baby, I am not going to stay on that site for long. About the only thing I can think of that might keep me on the site with a baby crying in my arms/lap is a promise of instant relief that I can try right then. You've got some YouTube videos along that lines, but there are too many choices and they don't establish you as the expert. In fact, you don't really show up on that page at all -- no story, no personal results, not even a picture.
D) I'm guessing you're not a doctor with 20 years of experience treating colic. That just means you may have to approach this from a different position than that of "The Expert" -- either the reporter or the trail guide might work in this case. Whatever you choose make sure that your page focuses on them taking a specific action. The .com has one action they are encouraging: register (buy). They even lay it out in 3 steps: 1. satisfy your desire for information, 2. learn our technique, 3. get started now! How goofy are those steps?! But I'll bet they work...
So there's my "summary"! (Can you imagine my full blown explanation?

)
Hope that helps.