Can these be "unlocked" or is it impossible, the phone in question is a nokia 6300 on o2. ??????????????????

I think that a method has finally been worked out for some of the BB5 phones, but I am not sure if it works for the 6300. Just keep checking on google is the best option

Yup, those can be done
The kit to do them is on the pricey side so will probably cost a bit to get done.

Jack