If by 'internal' you mean 'domestic' then my recollection is none - there has been a steady migration of slots from domestic operations (JER, LPL, EMA, BHX, IOM to name but a few) to international by either transference within the same company (i.e BD) or sale/exchange/arrangement between the domestic carrier and an international carrier.
Although I am no longer directly involved in slot requests/negotiations I would hazard a guess that the chance of allocation of any new capacity to domestics (which tend to need multiple frequencies) is the square root of b*@@%r all.
Brgds
TimS