I am wanting to purchase foreign currency (GBP to NZD) via a on-line service. I was wanting to know if there is a day of the week and or time of day that it is best to do this to ensure getting the best rate. For example: 6.30GMT Friday when the markets in New Zealand have just closed or 21.30GMT Sunday when the market has just opened in New Zealand. Basically wanting to know when a currency is usually at it's weakest