I feel the need to defend your planner! Planning and business rates consultancy are two very separate areas of expertise. A chartered surveyor who specialises in planning is not going to be able to give advice on business rates. It would be like asking a solicitor who specialises in criminal law to give advice on family law for example.
You can find a rating surveyor by searching
https://www.ricsfirms.com/ and filtering by 'rating advice'.
The VOA have a statutory power to compel you to provide information or face a fine of £100 (and further penalties if the information is still not provided). If you are at risk of a fine for non compliance, it should say so on the correspondence you've received. Either way if you ignore them they can come out and inspect the property; again, they have a statutory power to do so.
B&Bs are domestic property and therefore not liable for business rates so long as:
a. it is intended that within the coming year the short stay accommodation will not be provided for more than six persons simultaneously; and
b. the proprietor intends to have his or her sole or main residence within the property and the short stay use will be subsidiary to the use of the property as the proprietor’s sole or main residence.
How many people can you accommodate at one time in your B&B accommodation? Is it more than six? Is more than half the house used for B&B guests?
If you are assessed for business rates then you will still have a council tax assessment as well for the remainder of the property - you will be what is called a composite hereditament or mixed use property. The council tax assessment will be lower than your current one as it will only be for the residual part of the property.
You may well be better off being assessed for business rates so long as you can claim small business rates relief. Assuming this is your only business property, and the rateable value is less than £12,000, you will get full small business rates relief. The rateable value is based on the rental value of the business part of your property at a certain date (currently 1 April 2015). A business rates surveyor can help you estimate this. Or you could wait and see at what level the VOA assess you, and then if necessary seek a surveyor's help to challenge this.