Can't book appointment-Website doesn't work!!

I've been trying for weeks to book an appointment for a visa application as I heard you have to book well in advance. However the website has problem after problem, and I can't get past the previous addresses part of the application form as the 'add' button doesn't work. I'm overseas and I only have a small window of time to attend an appointment and now I'm worried I won't get a slot when I need it.<br> <br> When I called the call centre, the lady told me bookings for June aren't open yet and took my name and number so they could let me know when dates were available. Not wanting to be negative but I'm pretty sure this won't happen, especially as I had to give a New Zealand number to contact me on. And surely then I'll still have to fill out the form on the non-working website?<br> <br> I just want to book my appointment well in advance, as is obviously advisable and I feel that if this is the only way to get a visa, it should be functioning properly, because people's livelihoods and families are depending on it!<br> <br>