Although you've said it is an electrical burning smell, I suspect it probably isn't, since an electrical smell of that nature would surely result in some kind of ongoing electrical problem as well and yet the car seems to be fine.

I had the same symptom recently - burning smell in the cabin always noticeable when parking the car after a drive. In my case, the problem was a well known one and I notice you also have a BMW engine'd petrol V8 so the chances are it could be the same issue.

The problem in my case was failed pipes on the oil vapour recovery system. These pipes degrade over time, split, and then drip oil onto the engine block which then drips onto the exhaust. The fumes from the burn come up through the ventilation system into the cabin, but while you're moving they blow away. When you come to a halt they drift upwards and get sucked into the cabin.

Have a look here:

http://www.fullfatrr.com/forum/post98385.html

It takes 5 minutes and an allen key to find out if your pipes need replacing.

Thanks!

I do know my pipes were replaced sometime in 2009 and have the receipts to prove it.

However, there's no guarantee they haven't gone again and your description is very much like my own.

I'll check them later today or tomorrow.

Better book that garage slot. Free time isn't my best friend right now.  Si. <This is my name.

I eat rat poison.

A man ain't truly been insulted until he stands buck naked in front of a woman and she didn't even notice. Or care.

You'll need to describe the type of burning smell (sounds silly, I know). Burning brakes smell like burning clutch, burning oil is completely different, and an electric smoldering altogether different once again. And I'd find the latter worrying - especially in light of the 'pop' and all dead incident.

If you think it might be a caliper, check the other side front and compare. The wheels get warm quickly as you are turning 2+ tons worth of kinetic energy to heat energy, but they should be pretty equal side to side.

Burning oil and electric smoldering are very easy to differentiate if you've ever smelled either. I wouldn't know how to begin to describe the smells though: both are smoky and unpleasant but one, burning wires, is much more scary from an auto-electrics point of view (good description, huh? ). I would try to find the problem quickly. If it is electrical you could be putting your car at risk. I'd go so far as to remove everything that you did in replacing the wheel if nothing else can be found - and inspecting everything very carefully. 
RRC 2Dr, RRC 4Dr,
P38, and 2 L322s
(wife thinks I'm nuts - prob right, too)

Steve, thanks.

To be honest, I've ruled out the electrical smell. It's very definitely from the engine bay / wheel area on the drivers side. Particularly strong around the wing / bonnet aperture just after stopping. Dies very quickly right after switching the engine off.

Couldn't smell it when sniffing a few days ago with the engine running at idle.

Feeling the discs this morning, both were the same temperature.

The smell seems to be more oily than anything. To be fair, though, I've not smelt burning brakes since my wife set light to my 110's brakes on a steep mountain road descent in the Alps 4 years ago. I still get the blame for that even now.

But it's the (seemingly) intermittent nature that puzzles me.

Anyway, a slot is booked with BLR for next Thursday (their soonest available), but reading elsewhere in here, many recommend Guava in Guildford. Much nearer to where I work, so I'll call them later.

Thanks for the replies, so far. I'll keep an open mind on everything mentioned and suggested. Si. <This is my name.

I eat rat poison.

A man ain't truly been insulted until he stands buck naked in front of a woman and she didn't even notice. Or care.

As well as the top two oil pipes easily visible when you take the engine cover off, there are a couple of others - a very small one which joins the air separator to the sump and is only about 2 inches long, and a very thin bypass pipe that also joins to the same place. These are harder to replace so may not have been done in 2009. You need to check them all really. The point where the smaller ones connect to the sump feed is on the right hand side of the engine (i.e. the drivers side on a RHD vehicle).

Right, final post on this as the problem has been identified.

Cam cover gaskets are weeping a little oil.

I'm told it's not a common problem, but that's what I've got and the warranty company have said it's not covered under their policy. As I didn't pay extra for this, I'm not overly concerned, but it reinforces my belief that warranties aren't worth paying for.

So, that's one bill...

See my other thread for the next. Si. <This is my name.

I eat rat poison.

A man ain't truly been insulted until he stands buck naked in front of a woman and she didn't even notice. Or care.

Si, drop me a line.

Place the back of your hand against road wheel centres, if you feel one centre warmer than others, you'll have narrowed it down.