Locally to you there should be a wheelchair service assessment unit which your GP or consultant should be able to get you access to. they will assess your husband and make suggestions about what will best suit him. They can also supply a chair and may be able yo offer you a voucher towards private purchase if you want something non standard.
http://www.nhs.uk/NHSEngland/AboutNHSservices/social-care-services/Pages/nhs-wheelchair-services.aspx
There is likely to be a wait for an appointment.
Wheelchair retailers will let you go to their businesses and try chairs, also may offer to bring them to your home to try but at base they are salesmen, may not know a lot (or might be knowledgeable); might be pushy sellers.