Office 365

[#1]

We're trying to get Office 365 working with the domain that's hosted with PlusNet but can't get the damn thing to work when running the Microsoft "confirm that you own mydomain.co.uk". Problem is it can take up to 72 hours to populate the DNS servers so every time we change the settings we have to wait 3 days before we find it's wrong!
Currently we have our own server but want to test a trial of Office 365 and currently we have
Left field                         Type Pri Right field
remote.mydomain.co.uk. a         123.456.789.0
mail.mydomain.co.uk      mx 100 123.456.789.0
obviously domain name and IP address altered
and this works fine for remote access to Outlook Web Access and Microsoft Exchange respectively.
What we can't get to work is using what Microsoft advise.......
Left field                         Type Pri Right field
mydomain.co.uk.         MX ??  ms***********.msv1.invalid.outlook.com
Has anyone been able to get this to work?

[#2]

I assume when you say "It doesn't work" you mean that your email is accessible?  Are you typing ?? in as the Priority setting?  This should be a number.
Suggest you use an MX record check tool to see when DNS servers update?  Google 'MX record check' and take your pick.

[#3]

I think the right field entry needs a final . (full stop) added to stop the system adding your domain name to the end of the entry.
The post here is also relevant.