I've recently added SSL to a site and then admin area (with a left and main decorator, that redirects each request to https if just http).
But I've had to remove it because the site loads so slooooooow and often timesout and doesn't load at all - basically unusable.

Can anyone offer advice on whether this is "normal" or if there is something I can do to solve the situation please?

** bump **

any help would be greatly appreciated!

Can't you just set the base url to https://whatever and that fixes all other urls in the admin and on the site? The way you're doing it now you're essentially doubling all requests so of course that's very slow. I've not tried to run a site in SSL myself so I don't know but doing a redirect via decorator means that the whole stack loads before the redirect happens which is not a good thing of course.

Also there's Director::forceSSL() have you tried that?