Are these electrolytic caps? The 40 uF sounds strange; the closest you are likely to find is a 47 uF - as far as the voltage is concerned, use a cap that is rated at or above that voltage, and it should work fine (higher voltage caps are typically physically bigger than lower voltage ones, so keep that in mind when replacing them).
You should be able to find such caps (47 uF and 4.7 uF) fairly easily - for instance, this source (in the US):
**broken link removed**
Has them; for the UK, I would think RS, Farnell, etc - would stock these values as well (then there is Mouser and Digikey, which will have them)...