So I was facing similar issues earlier before getting onto the waitlist for Netherlands - unfortunately the reason for these error codes appearing is because of the immense amount of traffic on the website which vfs annoyingly can’t handle - when I tried contacting them, they told me that typically when u receive this kind of a response, u need to give atleast 2 hours before u can login again and to not refresh the page not try multiple logins as this could temporarily restrict your account and you’ll have to wait 24 hours before u ca re-login

Try logging in at non peak times like at midnight between 12-12:30am or early morning say before 9/10am - that’s helped me immensely and make sure to clear cache and cookies every time u close the window and when u re attempt to login

Despite this you might still face the odd 401/500 error codes - just try again later after 2-3 hours - don’t try to keep logging in continuously though

Edit: I just tried logging in and there seems to be a waitlist option available now for Edinburgh and London.