The Cambridge Weight Plan quantities, weights and measurements for all approved additional food are scientifically determined to complement the packs/plans. Every part of the egg, and the essential nutrients contained in that whole egg, will have been included in these vital calculations.
If the diet official guidelines say eggs they mean, whole eggs, not egg whites, alone. For all the calories and fats you may feel you are saving you are in fact losing the nutrients Cambridge expects you to include. For optimum health, that is. Once you start to tamper with the diet, decrease this, increase that, cut calories and fats, you are, as an earlier poster stated, NOT doing Cambridge as it is intended to be followed.
I have to say, and of course this is a personal opinion, that egg white only omelettes, which may be fine for competitive body builders and athletes whose 'training' diet includes vast quantities of albumen, whey protein, chicken, fish, and expensive vitamin and mineral supplements, strikes me as bordering a little on the obsessional for the average UK dieter, particularly one already seriously limiting food intake and calories on a VLCD.
I think perhaps you should run this by your Consultant for an informed opinion. Thereafter should you decide to continue with the egg white omelettes, fair enough. But there is a great deal of goodness in the yolk and it may be that you can ill-afford to do without it on such a restrictive diet.
All the best with whatever you decide x