I have been following your posts since last night, but have not been able to log into my account to answer as I'd forgotten my user name :(
Anyhow, it goes without saying that some of the things you have mentioned (the being told you must wear the female staff's uniform and that you must wear fancy dress on a given day) could be seen as intolerable.
To save answering in every post, I'm just going to put an over view in here.
1. If your company has a uniform policy it is part of your contract. Any changes to that uniform constitute a change to your employment contract (and being as you are in the UK) you have the right to review any contract changes and gives YOU the option of accepting or rejecting the changes. The contract CAN NOT be changed without both you and the company agreeing to the change. If, until this point your contract of employment (both written and verbal) have not included any details on charity fancy dress days, then stating you must wear fancy dress for this day is a change of contract terms.
Forcing you to accept the change without consultation is a breach of contract on the company's part. You have several options in this case. I have attached in the sources an ACAS document on varying the terms of a contract that may help.
BE AWARE, whilst you are under no obligation to accept contract changes, if the changes are deemed to be reasonable, the company may seek to terminate your employment.
2. Forcing you to wear clothing designed for women classes as bullying and humiliating. You are protected from this at work by law. This is something which you should take up with your manager in writing - let them give you a verbal warning.
By law they must document this verbal warning in writing (many managers simply think a verbal warning is a telling off). When this warning is received you must take the matter up with the company using their grievance procedure. The company failing to provide adequate uniforms is not an acceptable reason for them to give you a verbal warning.
3. With regards you manager insisting you call her Miss ..... That's her prerogative. If she feels that this will assist in maintaining the management structure, she is perfectly able to do this. It is a method that I have never personally used because it is generally only needed by management who are not confident in their abilities, nor their staff structure.
4. With regards to minimum age - IT HAS NOTHING TO DO WITH AGE! If you have not been promoted over the course of your employment, you should be asking why. Generally, people who shy away from requesting or seeking out promotion are ignored just as much as those who are not particularly good at their job. Particularly in a chain store environment.
I found it very difficult to progress my management career because of my age and attitudes like the one you portray above. I started managing company departments at the age of 18. By 20 I was managing a team of 15. Ages of those staff ranged from 17 to over 50. I never had any issues with the age factor. It is all about management technique and social skills. A manager who comes in asserting that they know best is often the worst kind of manger. Good managers listen to their team... Great managers talk WITH their team.
This is a case of 6 of 1, half a dozen of the other. Clearly, if your manager is acting the way it sounds in your questions, she is not a good manager at the moment - but that is why she is on the graduate management program (its a management training course, she is training to become a manager). On the other hand, you clearly are disgruntled at working for the company for between 10 and 11 years and not having been promoted to the management structure.
Often this does not happen, because companies make a point of not promoting to the management structure within the same branch. This is done to avoid issues developing with existing staff. If you want that kind of promotion, often the best course of action is to apply for a senior role in a near by branch or to change to another company for a more senior position.