(Original post by Zerforax)
To be honest, I think you've done the right thing. As soon as you commit to a figure or range, you'll either price yourself out or be way too long. You should be trying to get him to make the offer.
Ask for more information about the role (maybe ask for an email description) and then try and either phone asking more perceptive questions or alternatively try to get a face to face interview (all of this is good practice).
But to answer your question more directly:
The tax allowance this year is £7475 (rising to 8105 next year) so that amount will be tax free. After that you pay 20% income tax. You will also pay 12% national insurance.
So essentially you will pay 32% tax, add on 9% of income above 15,000 for student loan repayments.
If you are earning £20,000 - you would pay circa 2,500 income tax, 1,500 national insurance and 500 student loan (http://listentotaxman.com/index.php
So you would receive around £15,500 into your bank account. That would need to pay rent, bills, social life, food and everything else.
Rent is the biggest expense for most. You should check what rent would be roughly in Maidenhead for flat shares.
I probably spend £1000 on rent a month (live in London) and then another £1000 on bills and social etc. I'd expect Maidenhead to be cheaper and tbh I piss a lot of money away on stuff I don't need. You should be able to budget to half of that easily imo. (assuming rent would be around 125 per week/6000 a year, might be even cheaper! I have friends paying £50 a week for rent in the North)
So roughly assume around £1000 for rent + all expenses per month = around 12,000 a year.
I think you could survive on 15,000 but would be more comfortable on around 20,000. Heck could survive on less than 12,000 if your rent is very cheap and you're living on noodles.