@LovelyLovelyMe
Truly, what are the chances of winning anything ever with £500 worth of bonds?
It's true that PBs may not pay out at all for smaller amounts, but the more you have, the closer you are likely to get to the average payout. But if you do win even one £25 prize in a year on a £500 holding, that's a very good 'interest rate'.
Each bond has around a 1 in 33 000 chance of winning each month, I believe. So if you have £33k worth of bonds, on average you should win one prize each month, but in reality, it's likely to vary between 0,1,2 or very occasionally more than this.
On £500 your chance of winning each month is 500 in 33 000 = 1 in 66 so you 'should' win one prize every 5 years or so. But that's on average, so over a 20 year period for example, some people will win 4 prizes while others will win another amount of prizes between 0 and 10.
You can look at PBs as gambling the interest you would receive in a savings account. The best instant access is currently 1.15%, so the interest on £500 in a year would be a fiver or so. You can put your £500 in the NS&I income bond and claim your £5.75 a year in interest, or you can put it in PBs and bet the £5.75 that you might win more. Most people won't win anything but a minority will win at least a £25 prize.