BREXIT

[mtread]

I never realised that the UK had to introduce VAT in order to join and I also did not realise that 18% all that VAT we raise goes to the EU.Well that's even better then - leave the EU fully and every item with VAT will be 20% cheaper.So if VAT is harmonised how come its at different rates and on different products across the EU

The proportion of VAT we pay over to the EU is a major part of the 'membership fee' The so called £350 million a week '. All EU states pay the same proportional contribution. Its the way of making sure' bigger 'countries pay more than the smaller ones.
As to every item being 20% cheaper, I don't think your arithmetic quite works. Perhaps you could show your workings? 
All VAT in the EU is harmonised within boundaries, plus or minus certain percentages. Also what you can charge VAT on, and what you don't. EU 6th VAT directive.
It's to ensure that when you buy (say) Yamaha parts from Germany, you pay German VAT rather than have to reclaim it and pay UK VAT as an import.