We will not be obliged to give the EU £350million a week.
Yes we are. The rebate is taken off at source however that does not reduce our legal obligation to pay £350million membership fees to the EU each week.
That's why the UK Statistics Authority says £350m EU membership is misleading.
They would say that, wouldn't they. Anything to make it seem smaller. 
The UK's annual contribution last year was £18bn & the rebate was £5bn so we actually paid £13bn. But we got over £4bn coming back, mostly in the form of payments to farmers & poorer regions of the UK. Therefore our net contribution was around £9bn.
I think that paying our own farmers and poorer regions in the UK directly from UK tax payers funds is much more efficient than handing our money over to the EU and waiting for them to take their cut before sending it back to us, rebadged as EU money and with instructions on what we should spend it on.
Try doing that with your family's budget one month - hand it to a neighbour and let them take their cut before handing it back to you detailing what and where you're allowed to spend it.
And one day we may find that the magnamaous EU no longer gives us such a big rebate or decides to hand our money to somebody else - because once you give people power over your money there is always the chance that they will abusevthat power.
The EU could use that money (our money that we gave them) to punish us if we disagree with them in future, by reducing subsidies it our farmers. As for our poorer areas - there are many even poorer areas in the countries that are lined up to join the EU, like Albania, Montenegro, Bosnia. Perhaps the EU will think their poorer areas are in greater need if our money than our poorer areas are. Perhaps we will end up subsidising those poorer areas and our framers will just have to try to get by.
Trusting the EU with large amounts of your money and hoping that they continue to give some back to you is a very stupid idea. It does not make you safer, or stronger or better.
It makes you very vulnerable and very reluctant to upset your EU masters.