Strange one this, did you just renew from the quote you was given by post/email? Or was it a brand new quote?
On my renewals, I get quoted a figure which clearly states 'includes admin fee of £xx', so I'm surprised your renewal quote did not include the fee? Even calling up for a new quote, the quotes include this fee, why would they add it on afterwoods?
I rang them to ask what my renewal price was, got told 475 ish then i accepted that and told them to carry it on.