Employers are resposnsible for the health and safety of their employees when they work from home and muts carry out a risk asssessmnet as well as a DSE. Does the same responsibilty apply to consultants and contractors when they work from home for the company ?

Rather simplistic rule for responsibility follow the money aka "who pays" the worker

If you pay the individual you are the employer with all employer responsibilities

If you pay a company (even an individual who has set up a consultancy) who then pays the employee (including the business owner) THEY have the employer responsibilities

If it is ongoing for a protracted period well written contractual arrangements should describe responsibilities

I wouldn't rely on the "follow the money" approach.  There are lots of reasons for using contractors, and in many cases you may still be viewed as the employer for safety purposes. 

In this case if the contractor or consultant is a sole trader you would actually be paying them directly, but I doubt you would consider yourself to be the employer if they are working from their own home.  There is probably no clear destinction and each case will have to be judged on its merits.  Even if you decide you have some responsibility I doubt you would need to do more than state that they should be aware of the risks and seek advice if they felt it necessary.