Virgin came to my area about a month ago, I ordered straight away and at the time it said the best package I could get was M200. But I just looked at the postcode checker again and now it says I can get M500, but when I sign into my account and go into the upgrades section, It just shows packages with M200 & TV. Do I have to wait until after we pay the first bill or is postcode checker lying?
Whilst not conclusive, experience of customers in these forums is that Virgin Media actively avoid promoting the obvious availability of faster broadband and phone only packages except where they can up-sell a TV package with it. In my case, logging into "My Virgin Media" (where you manage your account), it says my 200 package is the fastest available, but having spoken to sales agents I know that if I wanted it there's 500 Mbps available.
If you phone VM on 150 and select options that take you through to "upgrade my package" you'll get to speak to sales agent who can tell you what options are really available, but this assumes you're already connected with a live account. If you're waiting for installation, then my strong recommendation is not to confuse what is already a fragile and disjointed process.
The other thing for you to consider, is what makes you think you will make any worthwhile use of 500 Mbps? The biggest single use of bandwidth is watching 4K videos, and there's limited content available, and no point on watching that on small screens. If you've got a household of six people, and they're all watching different 4K videos on 60 inch TVs at the same time, you've still only used up 150 Mbps of bandwidth.
Don't get me wrong - it's your money and your choice, so by all means pester VM for a 500 Mbps connection if you want one, but I'd suggest you get your 200 Mbps connection installed and working, see how often you're inconvenienced by the speed, then decide if you want to give VM even more money (and more still when the new customer discounts end).