It's so handy being able to nip down the middle of two-lane standstill traffic
How do the coppers view this and overtaking slow traffic though?
The fact that you have to ask the question concerns me a little. Be very careful.
It's called "filtering". It isn't illegal in the UK but in much of Europe and the Americas it is. That's probably because it isn't always safe. The police will take into account your manner of driving if and when they act. A traffic officer is a very highly trained driver. I've been out on bikes many times with serving traffic officers and they are absolutely amazing. They can assess your skill level in about three-quarters of a second, and if one pulls you over and gives you advice it's because he's seen things which concern him and you need to listen. It's for your own good, and everyone else's. He doesn't want to wipe your blood and brains off his uniform before he can go home for tea, I can assure you. And he's probably done that a few times in his life already.
I filter, sometimes in conditions and at speeds which might alarm you, but I'm taking great care when I do it. I know what the bike can (and can't) do, and what I can (and can't) do, and what the vehicles all around me can (and can't) do, and I'm constantly trading off the safety of my current situation with the situation that will unfold as I progress through the traffic. It takes a lot of practice, and you have to be able to completely forget about controlling the bike, it has to be like part of you. It takes some time to get to that level of comfort with a machine.
Many times when I've been on the Peripherique (Paris ring road) I've seen people on scooters and mopeds filtering in conditions and at speeds and with apparently so little care that I could only call it suicidal. Most of them are wearing jeans and sandals. It's terrifying. So I do relatively little filtering in Paris because it's so dangerous. Places like Bordeaux and Toulouse aren't as bad but they're still to be avoided if possible.
A few years ago on the Hayabusa I filtered to the front of a stationary queue at a red traffic light on the A38 in Derbyshire, and stopped. I waited for the light to turn green but the driver of the Mercedes van behind me didn't. He did several thousand pounds worth of damage to the bike when he pulled away but fortunately I managed to avoid being pushed under the bus that was crossing at the time.
As you gain more experience you'll start to ask less about what the police will think and more about what's safe, fluid, economical and courteous. When you've a few years' of experience under your belt I highly recommend getting on an advanced riding course run by the police if you can. Many of them are free, because it's more enjoyable and a lot cheaper than cleaning up the broken bodies and bits of plastic after another RTA involving a bike.
Filtering is a particularly tricky operation, partly because it brings you very close to tons of machinery which can inflict terrible injury and partly because you can "appear out of nowhere" as drivers often say just after they've wiped out a biker while changing lanes. Great caution is needed. I might have mentioned that short of jumping off Brighton Pier at low tide, riding a motorcycle is by a long way the most dangerous thing you can do in peacetime. Everything you do on the bike will tend to increase or to decrease the chances of your getting to your destination safely. That's true of if, when and how you filter.
Must rush now, sorry, have to go eat a pizza.
