Is there a number we can use for uA/MHz on the LPC17xx? I am currently running at 25MHz, and would want to increase to approximately 48MHz, but I am not sure how current-drain will be impacted.

[lpcware-support]

You can use a value of 450 uA/MHz as a rough value. Refer to LPC1700 low power mode app note which provides some tips to reduce the current.