John Innes No. 3 would be best - but it makes the pot very heavy. You may need a larger pot too...

If its been in the same soil for years the level might have dropped and if so you might get away with just top dressing it with John Innes no 3 for now.

Thanks guys, i have a very large pot and number 3 it is. I'll fetch it this morning.

Hank, you've asked whether you should turn the plant out of the pot and remove as much soil as possible, gently, and then repot in the new compost. You also said the garden centre told you to feed it with tomorite (dear lord..).
First, let me say that tomorite isn't something that's at all suitable for a long term shrub grown principally for its foliage and not for its flowers. Tomorite is specifically designed for tomatoes, has a very high potash level to encourage lots of flowers and thus, fruiting. The garden centre staff want taking out and shooting...

As for the first part (removing compost) yes, that's what you need to do, but unfortunately, you may find the rootball is completely solid with just roots, and its not possible to remove any soil, or at least, none that makes much difference. In that case, you have a choice - you either risk cutting some root off (very risky) and repotting, buying an even larger pot and repotting, or finding a place in the garden for it, should you really want an enormous, dense shade giver like a bay tree in the ground.
As far as feeding potgrown shrubs like this is concerned, a general purpose, balanced fertiliser such as Growmore will do, raked into the surface of the compost in spring, or after you've removed the surface compost, when you add the Growmore and top off with fresh compost. Alternatively, a liquid balanced feed such as MiracleGro general purpose (the box with blue powder in it) applied in April and again in May.