Ganesh, a small fee could be £10 for one policy, or it could be £100 for ten policies, it depends on the workload involved. And the whole point of a broker is that they do all of the form filling etc for you, you just have to spend a bit of time answering their questions, and you would do this once and they would approach a number of insurers on your behalf. If you have ten policies, rather than just one or a couple, there would be a much greater workload, and more chance of them having to spend time during the year sorting out claims etc on your behalf, and so the fee would be higher.
The benefit of the broker option is that you get professional advice and should get a claims handling service also. Because of the size of some brokers, or those part of bigger networks, the prices you can get are often cheaper or equal to those found via other channels (and that includes the fee). The policies a broker usually sells are often of a higher standard than those found online, with higher limits, lower excesses, and wider cover and so is always worth obtaining a quote for comparison of service and price. (And I dont mean ask me for a quote, you should approach one of your local or regional brokers, they will provide a local friendly service in most cases with the benefits of providing local knowledge)