Don't worry... I was rejected for a job after passing 5 interviews, because the organisation wanted to change the job spec at the last moment and I didn't qualify.
I argued that I fully met their original requirements and it was unprofessional to change it this late in to the game. The organisation insisted on advertising at a £5k higher salary (to attract a candidate with that level of qual), so I told the recruitment agency that approached me that I was ****** off. After about 3 weeks of radio silence I had a call to get offered the same job... weird
Anyway, congratulations. To be honest with you... if I knew I was the only candidate at that salary I'd have pushed for that extra £1.5k... are they really going to quibble over paying you an extra £29 a week gross pay?