disease in bramley apples

Most likely it is Common scab. This starts off on the skin but does work its way into the flesh as the apple ages and ripens. If you catch it in time you can still use the undamaged part of the flesh.
To stop it, next year spray the tree with either a suitable fungicide according to the info on the packet. Or spray the tree with Copper sulphate (Bordeaux mixture, it is sometimes sold as), every two weeks from when the fruit first forms.

I think this is Bitter Pit. Often found in apples bought from the supermarket.
You can google this for full information, but if you are cooking them don't worry about it as it is not harmful.

I think that Bitter pit is more likely Rob. Especially as Bramleys are very susceptible to it. The cure (but as you say, it is not harmful) is easy. Just good husbandry. Look after your tree Mike. LOL.

John.

If it is Bitter pit then the trouble is a Calcium deficiency.

Yes Boggy. The RHS advice is at this web page.

http://www.rhs.org.uk/advice/profiles0901/bitter_pit.asp