Using the Forgotten password option didn't recognise my email address when I put capitals on each name (which I normally do), but I know that the unique user validation is not case sensitive. Would it be better to retrieve the email address with a non case-sensitive search?
The issue here is whether e-mail addresses are case-sensitive.
And the answer is yes, they *might* be.
joe@bloggs.com
The domain part of that ( blogs.com ) is not case-sensitive.
DNS will find the MX record for the domain OK either way.
But the username ( joe ) which the mail server has to deal with might be.
It's OK for the mail server to be case-sensitive.
Some are, some are not.
So it's a Bad Idea to make a general assumption that e-mail addresses are case-insensitive.
Websites that ask for e-mail addresses should accept them as-typed, and not mangle them into what they think the user meant.
The solution to your issue is to be consistent in your use of case, and not expect websites to fix up your inconsistencies.