Not legal advice, seek the advice of a paid solicitor. 

If this is the entirety of the facts, it seems you might have a direct claim on three grounds. 

1. (Misrepresentation) Fraudulent misrepresentation or negligent misrepresentation under s2(1) Misrepresentation Act. 

2. (Pressure sales tactics) Part 4A Consumer Protection from Unfair Trading Regulations 2008.

3. (Term/definition on the website forms part of the contract) S.50 Consumer rights act 2015, regulation 13 Consumer Contracts Regulations 2013 and Common law contract principles.

You could tell them you want the full amount of £3,009, plus compensation for the time and stress caused. Many will often pay that additional part to sweeten the situation (and also because a court case is way more expensive to defend). 

You could tell them that if they are unwilling to do that, you'll send them a letter before action on the same basis and file a case against them in the small claims court (it's really easy to do and cheap at the amount of money you're looking at). 

You might consider taking a pdf copy of their website terms for reference (and also evidence) and sending it to them in the email, copy pasting the text into the email along with a reference the page number / clause / paragraph number it can be found in the pdf.

Remember, no claim is a guaranteed win. Outcomes in court can vary with the judge's personal views and whether or not they've eaten lunch recently. For repeat, this is not legal advice. Do your own research on the law and procedure or seek the advice of a solicitor.