Realism hurts, I get that.
You really don't. You are failing to recognise that the UK is the 5th largest economy in the world. You are using the Nick Clegg argument that the UK is too small and uninfluential to make it alone in the world. You are wrong.
We're a big economy, but we are one coming out of a deep recession and one that is heavily reliant on EU trade.
In comparison to many EU economies the UK is actually booming. The overall EU is the only trade bloc in the world that is actually shrinking, apart from Antarctica. There is a lot of business that we could be doing globally but are prevented from doing so by our EU membership
If we leave the EU and services in particular become cheaper for our EU export markets within the EU, due to tariffs, than from us, then it is us who will pay the price.The country we were exporting to will pay a little more, or get a slightly lower quality service (or product). The cost to the UK would be significantly higher.
There is no single market in services. You appear to be blinded by the idea of one-sided tariffs. Countries do not impose tariffs lightly. With tariffs come penalties.
Your whole argument appears to be on the false idea that little weak UK should be so happy and beholden to the wonderful EU that deigns to trade with it. Nothing could be futrher from the truth. Outside the EU we would be the EU's biggest trading partner. You do not place punitive tariffs on your biggest export market unless you want to see a huge decline in exports and a rise in your domestic unemployment.
Equally, with elections looming for a number of EU member states with their own anti-EU parties, the governing parties will not want to give Britain an easy ride in agreeing a trade deal or accession to the EEA that is not significantly less advantageous to Britain than our current membership of the EU.
With elections looming any Government is desperate to get its unemployment figures down. Treating the UK in the way you describe would have the opposite effect so we can safely assume that this will not happen.
The stakes are much higher for Eurozone countries when it comes to the imperative to keep the EU together and they will want to make an example of Britain to their domestic political audiences.
The stakes are very high for the Eurozone country as the loss of the UK's net contributions to their economies and the UK's absolution from having Eurozone bailout costs placed on it by the EU will be keenly felt by the EU and will be celebrated by the UK.