Reduced rate VAT - conversion of residential to house of multiple occupation

I have tried to call HMRC VAT for hours and days. Each call takes 30 minutes to answer and then once I get through it cuts off. There is no webchat and absolutely no other stated way to make contact. How can this be acceptable? I am look for information on what certification is required to ensure suppliers charge a reduced rate of 5% VAT in context of conversion of a residential home to multiple occupation (according to paragraph 7.5 of guidance Buildings and construction (VAT Notice 708)). Is there a template certification that I can download and provide to suppliers (please note we have since purchase of the relevant house commenced an application to the planning authority)? Also, since purchase (several weeks ago) of the house we are converting, we have incurred standard rate VAT with solicitors and architects and would wish to revert to them and ask for a refund of 15% of the VAT we have paid and that they adjust their respective VAT returns. Is this possible to do and what are the requirements to ensure proper processing.

The reduced rate (5%) only applies to conversion services relating to the physical conversion of the property (materials and labour), it does not extend to professional services such as architects and solicitors. Notice 708, section 7.6 confirms this so you cannot go back to the Architect/Solicitors and ask for a reduction of VAT previously charged. Section 18 deals with certificates but these are not required for a conversion to a HMO in most cases, certificates only usually required if the dwelling is going to be a "relevant residential dwelling" and "relevant residential" means a care home or old persons home, prison or similar, so it depends what you are intending with the finished property. As for contractors, usually a copy of the planning permission/consent should be sufficient to give the contractors the comfort they need to reduce rate their supply, which the contractor can hold on file should they ever get a VAT inspection.

Hi Saul Greenberg,
I'm sorry you are having such problems getting through to the Helpline.
Please see below for all the various ways you can reach us.
VAT: general enquiries
Please make sure that the conversion meets the requirements of a qualifying conversion as per the following guidance,  section 7.2 
7. Reduced rating the conversion of premises to a different residential use
If the conversion is a qualifying conversion then the builder should be able to apply  5% VAT  to the building work.
The builder would need to see evidence that a qualifying conversion is taking place so that they can keep this evidence in their records.
A council planning reference,architectural drawings would be evidence that builder would normally ask for.
The 5% VAT would apply to most of the work but would not apply to professional services like solicitors and architects.
Please see section 7.6 of the following guidance:
7. Reduced rating the conversion of premises to a different residential use
Thank you.