Policy holder hiring own solicitor

i just wanted to know if its possible for an insurance policyholder to hire his own solicitor in handling his case instead of using the insurance company lawyers? will that be going against the policy thus rendering it null and void,or would i still be able to claim under the policy?

Also,is there any law or case that says I cannot claim costs of proceedings from my insurance in the event I do lose the case(when using my own solicitors)?

i really need help...and any assistance or light shed on this matter is greatly appreciated.