There's something called the 28/36 Rule. It's a bit biased toward the U.S. tax structure, but should give you at least a ballpark estimate for what you can afford in the U.K.
The rule is that you can spend up to 28% of your gross monthly income on housing expenses (mortgage, any housing taxes, utility fees, etc.). And no more than 36% on total debt.
In your example, you make £2,000 gross income a month. That means you can afford up to £560 on housing (rent or mortgage, plus all taxes and utilities). You can afford up to £720, or an extra £160 (if paying the full amount on housing), on debt. That debt may be credit card payments, car loans, that sort of thing.
I'm not sure how much your utilities and housing taxes would come to in the U.K. Let's optimistically say only £60 per month. That leaves you with £500 for a mortgage payment. With that, you could afford roughly a £100,000 mortgage, on a 25 year-term.
That roughly matches my personal rule-of-thumb (in Canada), which is that the upper limit you should consider is roughly 4 times your gross salary, assuming you have no significant debts.
Now, you can go with a longer mortgage term. In Canada, the upper limit is 30 years, but it looks like longer terms may be available in the U.K. That would lower your monthly rate by a bit, meaning practically you could afford a slightly larger mortgage.
Barclays Bank claims they'd consider lending you up to £107,760 based solely on an income of £24,000 per year. Looks like they'd require 10% downpayment, which again indicates roughly that you can afford approximately £100,000 (except not, because you'll need to pay closing costs). If houses in your area cost £200,000 to £450,000, I'm afraid they are well outside your price range.
By comparison, when I bought a house seven years ago, I was looking at roughly $300,000 - $400,000 (dollars, not pounds). Our combined income was somewhere around $150,000 at the time. We could afford our price range but I wouldn't say it was easy.
