Good that you dropped in. Hopefully this will prove to be a good place for you to be.
The easiest thing to do is go to the web site for a given brand or find the items on a department store web site. There will usually be a size chart. There will also be instructions on how to take your measurements. I do not recommend that you trust numeric size designations or the small, medium, large thing. There is no such thing as standard sizing in women’s clothes. That covers between manufacturers and even within a given manufacturer.
I often recount a personal experience. I have 5 dresses from a brand by Sharagano; same style and same fit. However, the labels say size 16, 16W and 18. So much for consistency!
Now, contrary to what I said, I have found one brand to be very consistent: Gloria Vanderbilt. I assume that they are sold in the UK. What I have found is that the Amanda style has been so consistent that I don’t try them on anymore before I purchase. I have several pair. Some were purchased new and others from thrift stores. However, the last pair that I bought was at least 2 years ago, so hopefully their sizing is still consistent. All of my Amanda jeans are size 14 and fit the same way. Some of the Amanda style have rear pockets without any fancy stitchwork. Those can be worn in either male or female mode
Regarding therapy, it is important to find someone who has experience with gender issues if you choose to explore that. Many who are very good therapists otherwise, may not have that particular experience. Are there any LGBT Centers near you? Many, here in the US anyway, have therapy services as part of what they do.
Thanks for completing your Profile page. It really helps others to understand what’s happening for you and where you may struggle.
If you want to search for other members who my be nearby, click on Social in the menu and then Member Directory.