Yes, this would be advisable. Otherwise you will be bound by the contract even if the reference is unsatisfactory, and will have to give full notice to terminate.
Be careful that your requirements are not discriminatory, particularly as regards the medical evidence, otherwise you could fall foul of the disability discrimination legislation. You must ensure that the level of fitness required is not in excess of the requirements of the job, and if you are thinking of taking on someone who has a physical or mental impairment that may amount to a disability, consider the issue of 'reasonable adjustments' under the Disability Discrimination Act.
Note, too, that the 'default' retirement age for all employees (both men and women) is now 65 - which means that it is illegal to require anyone to retire earlier, unless you can show why early retirement for all employees doing this work is appropriate or necessary. The 'default' age itself is being challenged before the European Court (the 'Heyday' case), but since there is unlikely to be a definitive ruling before 2009, it is reasonable to rely on it for the time being.
Do not ask for excessive information in checking on the applicant's work history or medical record, and ensure that you have his (or her) consent to take up references and obtain medical data. Otherwise you could fall foul of the Data Protection Act 1998.
