I had a look on HMRC's website & this is what it says:
Which equipment and services can be bought without paying VAT?
If you have a long-term illness or you're disabled, you won't have to pay VAT when you buy any of the following items:
adjustable beds, chair lifts, hoists and sanitary devices
auditory training aids
low vision aids
medical and surgical appliances designed solely for the relief of a severe abnormality or a severe injury
alarms
motor vehicles, boats and other equipment and appliances designed solely for use by chronically sick or disabled people
You also won't have to pay VAT on any charges made for the installation, repair and maintenance of these items, or on any spare parts and accessories needed for them.
Certain building work may also be VAT free. This includes building work on:
ramps, doorways and passages
bathrooms, washrooms and lavatories
lifts
If you need to have any general purpose goods adapted for your use, because of your condition, anything you pay to have them adapted will be VAT free, but you'll still have to pay the normal rate of VAT on the goods themselves.
Also, if you're over 60, then you may not have to pay the full standard rate of VAT if you get certain mobility aids installed in your home.
I guess from the underlined paragraph, you'd be hard pressed to get the VAT back on shoes & could only reclaim the VAT on adaptations to them to assist your medical needs.