the likely cause of your whitish discoloration of your throat is a yeast infection of your throat...
yeast (candidial) infections are pretty common after antibiotic use.. what happens is that when we take antibiotics it kills some of the good bateria as well... these bacteria normally prevent infections with other organisms such as yeast...
you can take nystatin which i presume is available over the counter in UK.. it will resolve in a day or two
let me know if you need more input
regards
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