If you need UK immigration advice you may obtain it either from a solicitor or a registered immigration adviser.
Any solicitor is entitled to provide immigration advice on a privately-paying basis, but only solicitors who have passed certain exams may provide legally-funded immigration advice.
If you intend to instruct a solicitor on a privately-paying basis, you are strongly advised to ascertain that they are experienced in immigration work.
If you intend to instruct an immigration advisor you are strongly advised to check that they are registered with the Office of the Immigration Services Commissioner (OISC).
You may ascertain this by visiting the OISC website, on http://www.oisc.gov.uk.