Hmmmm. Thanks everyone - you have given me a good start.

You can't really go blonde successfully with a pack - it takes quite a bit of hairdresser work (numerous visits) to go lighter and have it look nice. What are your eyebrows like? Are they dark or light because blonde hair with dark eyebrows is a bit obvious.
Oh, I definitely won't be going with a pack. The thought makes me shudder My eyebrows are pretty light.