We modelled the isothermal crystallisation of oxide glasses during their phase separation using the static Monte Carlo technique as in the site percolation model. Initial compositions such that crystallisation can only occur in the evolving glassy matrix phase were considered. The isothermal crystallisation behaviour in terms of model analogues of crystal nucleation and growth were found to qualitatively correspond to the experimental results. The percolation behaviour of the crystalline phase in the evolving glass-ceramic was then studied. The validity of the scaling assumption for percolation phase transition was first tested for the considered systems and then various critical exponents at and near the percolation threshold was estimated. It was found that scaling hypothesis followed for all cases considered in the present investigation.