Royal Mail is regulated by OFCOM who state:
Royal Mail Customer Service Centre, FREEPOST, 20 Turner Road, St Rollox Retail and Business Park, Glasgow. G21 1AA
Tel: 03457 740 740 (textphone 0846 000606)
Royal Mail customer services [personal.help.royalmail.com
If your complaint cannot be resolved, the operator can issue a Ďdeadlock' notice that will allow you to ask the Independent Postal Redress scheme to investigate your case - [www.cedr.com
The scheme can only investigate complaints about Royal Mail's regulated postal services. If your complaint is about a non-regulated service and you are still unhappy with Royal Mail's response, you should seek independent legal advice.
former Liberal Democrat Councillor for East Dulwich Ward (2006-2018)