Hi,
I get the feeling that it has something to do with new customer discounts? When you change your policy you have already been hooked and therefore no longer eligible for the best deals.
I had a similar issue and got quoted a ridiculous fee, with admin fees ranging from £150, £1,25, £75, £25 and £15 plus the new inflated fee. The irony is on the policy is sates the fees to change the the policy is £26.50! I just kicked off and they soon dropped to less than half the original quote. Just to avoid the hassle I have renewed but fully intend to switch at the end of the year. All the companies are the same. just keep switching and get rewarded for being disloyal.
They are just a bunch of lying money garbing sales men that will take whatever they can from you, they don't give a dam about you or providing a good service, they just what your money.
I feel for youngsters getting insured for the first time, my daughter had a quote for a ford KA over £10K !!!!!