Voiceability are an excellent advocacy service, though I don’t know whether they cover your location or specific question - you can check on their website https://www.voiceability.org/
Belinda Blank of The Advocacy and Support Partnership http://www.advocacyandsupport.co.uk/ is very knowledgeable. I think they may only deliver services around North London but she may be able to point you in the right direction for more local support.
Depending on where you ware based, it might be worth looking for local advocacy services through https://www.theadvocacypeople.org.uk/ or https://www.pohwer.net/Pages/Category/in-your-area - they are commissioned by the NHS for support but they are independent charities.
Wishing you the very best of luck.