Recent events are weighing on the minds of British voters facing a planned referendum on continued membership in the EU

For years, European Union mandarins in Brussels have touted two things as successful achievements for the body - the single currency, called, unsurprisingly, the euro, and the Schengen Agreement on free movement within certain member states.

Well, both are looking a bit rocky at present and that's having a knock-on effect in the United Kingdom, where voters are bracing themselves for an in-out referendum, possibly this year, maybe next year.

Let's take the Schengen Agreement first, named after the small Luxembourg town where officials first negotiated the plans for a borderless Europe back in 1985, when five of the then 10-nation strong EU agreed to abolish internal border controls within the states signing up to the deal.

It took 10 years to implement - well, this is the EU - and now 22 members of the expanded EU have signed up for Schengen, plus four non-EU members. The UK remains resolutely outside Schengen.

What it means is this: anyone traveling between Schengen member states can cross borders freely without any checks or border controls. In addition, visitors from, for example, China, need only get one visa that covers them for pretty much all of mainland Western Europe.

It took the massive influx of migrants - either fleeing war and conflict in Syria, Libya, Iraq and Afghanistan or those simply seeking a better life - to bring Schengen pretty much to its knees.

Last year over a million migrants, some genuine asylum seekers, some so-called economic migrants and a minority, a very tiny minority, of potential terrorists, made the perilous sea crossing from Turkey to Greece, or from Libya to Italy, in a variety of rubber dinghies, worn-out motor boats, and decrepit fishing vessels, most of them victims of people-smugglers who would charge them around $2,000 a head, sometimes more,

It's that influx that has pretty much left Schengen moribund. Virtually all the arrivals wanted to go to Germany - Chancellor Angela Merkel said last year that Germany would open its arms to arrivals - or Sweden.

Last year's twin deadly attacks in Paris, with suspicions that Islamic extremist gunmen used the migrant route, mean stringent checks have been reintroduced on most internal borders within the Schengen area.

Schengen itself relied on the external borders of the EU being rigorously policed, but as one who has often just been waved through when traveling by car between non-Schengen UK and France, I can say that wasn't the case.

The mass migration issue raises another question - the EU's ability to act as one in deciding on a common policy.

Well, it's been over six months now and the EU members and faceless bureaucrats in Brussels are arguing over what to do.

First, they decided to throw money at it, offering aid to Turkey and Greece to try to control the flow. A waste of time - they still come at an average of 1,000 to 1,500 a day.

Options proposed by various member states include a giant fence sealing Greece off from the rest of Europe, fences along the borders of the various countries the migrants pass through on their way to Germany, and a rewriting of the rules of asylum.

Other suggestions include a quota scheme for all European countries, a proposal rapidly rubbished by many states. Both Sweden and Germany have said unsuccessful asylum seekers will be sent back.

Which brings us to that other tottering pillar of EU achievement, the euro.

When the single currency was first introduced in January 2002, many, and I include myself among them, questioned how it would work.

I'm no economist, as both my wife and my bank manager will testify, but I cannot for the life of me see how a single currency can cover such diverse economies as the mighty German model and the frail southern European examples, including Greece.

It being the EU, of course they bent the rules to allow the likes of Greece, Portugal, Spain and company join in the spirit of a united Europe.

Inevitably, Greece's ramshackle and lopsided economy fell into crisis, and had to be bailed out. Speculation two years ago was rife that this would mean the end of Greece's euro membership, but a series of massive loans and pledges of remedial action from Greece papered over the cracks as the EU bureaucrats once again kicked the can down the road.

One of the conditions of international lending to Greece was the sale of state assets, and here China has been the main beneficiary as it snapped up the port of Piraeus, a move that will lead to further Chinese investment and involve Greece in President Xi Jinping's Belt and Road Initiative.

All this is weighing heavily on the minds of British voters ahead of a planned referendum on continued EU membership. Most Brits, myself included, like the idea of membership in a trade-oriented European body, with freedom to travel.

What we don't want is to be dragged into a United Europe, with control of laws, politics and everyday life being handed to an unelected few in Brussels.

That's why Prime Minister David Cameron is trying to secure a deal that protects UK sovereignty, while still remaining a member of the European club.

It's going to be an interesting few months.

The author is managing editor of China Daily Europe, based in London. Contact the writer at chris@mail.chinadailyuk.com