One thing that is likely to change is that Facebook et al. will find it a lot more difficult not to pay taxes on the revenue they make in UK.
I don't actually think so.
What can the Government do to make that happen? Lock FB out of the Internet?
They may try to fiddle with VAT rules to make sure the UK advertisers paying FB cannot zero-rate it but in the end the cost will be on those advertisers and not on FB.
This may affect some other, non-internet related companies, currently structuring their tax affairs via the EU but if it will affect them too much for comfort - they'll just leave.