LED lamps are very voltage tolerant . Some have a voltage range from 9v to 18v others I have seen from 8v to 36v . This is one reason they have been used in control instrumentation for many years . A quick search on ebay gave me a price a price of an Mr11 -12led £7.24 uk delivered ,and £2.87 delivered from Hong Kong . Both looked identical , and no mention from either of a built in regulator .Another point , any modern built Motorhome should have it's 12v D.C. output already regulated by the manufacture .
LEDs by themselves are current devices, not voltage devices so either need to have a current regulator in series to limit the current to a safe level - often about 20mA per LED - in which case the lamp can be made to tolerate a fairly wide voltage input range - the 8V to 36V referred to, OR they can have a current limiting resistor in series with each series string of three (for 12V operation) in which case they are very voltage sensitive and an increase in supply voltage of a couple of volts, may double the current flowing through each LED. Since they have very little capacity for getting rid of excess power generated, they don't last long and this has been a major sticking point to more general acceptance. With current regulation becoming the standard, voltage intolerance and short life should be a thing of the past. Trouble is, just how does one know which has a current regulator. I guess if the specifications say it does, or if they are sold with a wide voltage range, then that is a good sign, but other than that there is no way to know except by buying some and testing their current vs supply voltage characteristics. Price is NOT a good indicator.
Claimed super-long life hasn't materialised either and it is pretty easy to find trucks with tail lights having groups of three LEDs dark even though they are the wide voltage current regulated type.
Haven't heard of many motorhomes with regulated DC habitation supply. Some - older types - have voltage converters which are fixed 13.7V, but seems to me the trend is away from those
battery killers and more towards decent three-stage chargers which can produce charging voltages up to 15V in equalisation mode and 14.4V normally. Blowing an occasional $3 bulb doesn't come close to wrecking $1000 worth of batteries so I prefer a three-staage charger anytime.
This is why better quality lamps have current regulators instead of series resistors.
I'm not a big fan of LED lighting - only because until fairly recently their so-called warm white was invariable more like blue daylight, but now that their warm white is a lot more to my liking - although still a bit monochromatic - I have tried a few different types with reasonable results.
To replace the fluros, I've ordered a couple of these from Deal Extreme
80310 12W 3500K 800LM Warm White LED Emitter Metal Strip (12~14V)
to see how they go.
Another problem you will stike and already alluded to is that although the surface mount device (SMD) LEDs have a beam angle of 135 degrees, normal lamps are a lot less glarey (not the extreme pinpoint source of a LED) and have a wider beam so in my opinion give a more pleasing, less contrasty atmosphere than LEDs. Better design of lighting fittings may solve the problem but not yet.
