The requirements for medical certification to fly gliders in the UK are currently governed by the BGA and in addition to the aforementioned medical certificates you can also use a current driving licence to go gliding solo in the UK until April 2020.
From what we know at the moment (January 2020) this is probably going to continue, but it’s worth checking the BGA website for future changes. For those wanting to fly passengers or instruct, a higher medical standard is required and details for this can be found on the BGA’s website. It is very important to make sure that you check for flights after April 1 2020 what is in place as in principle a LAPL Medical and LAPL Licence will need to be held, unless the exemption is extended which allows national licences to be continued to be used. For more information on medicals go to www.caa.co.uk.