I deal with people in the UK, the USA, and occasionally Japan. I'm having problems with accounting at the moment since the software I use doesn't take multiple currencies so I am having to convert everything into pounds.

As far as I'm aware, the main thing is to be consistent in how you do the conversion - is this correct?

I am working on the method that as soon as funds leave my account, I do the conversion, and as soon as funds enter the account, I convert them too.

The problem there is that sometimes I get paid into paypal in dollars, and if I convert the amount into pounds on the day they enter the paypal account, I'm not sure what to do after that - if I withdraw the money a while later, then what if the conversion rate has changed?

How do other people deal with this issue?