There are transformers and there are inverters often also called transformers. With a transformer it is simple unplug the tungsten and plug in the LED however with the inverter there is a minimum as well as maximum so they would require changing.
Transformers are heavy and inverter is comparison are light but I have tried to work out a way to work out which are fitted without finding the device and other than measuring the frequency which is well beyond DIY can't think of a way without reading details on the device or feeling how heavy they are.
The other point is angle of beam. Spot lights are as name implies designed to give out a spot of light but the angle of that spot varies and although you can find with the more expensive lamps the angle often you don't know until you fit them what the angle is.
Where a transformer change would be required then moving to GU10 would mean no transformer is required but that means some re-wiring.
Bulb prices vary from a 0.58W (read that as candle) from Pound World at yes you guessed £1 to a pair of 1.4W lamps from Lidi at £5 to £17 for a 5.5W from
screwfix.
As the size increases the price sores Toolstation do a 7.5W at 40 deg angle at £16 and it is the angle which can present a problem and for spot lights to be used as general lighting one has to bounce the light off a white surface so this may be the time to fit more appropriate lighting.
In general the low output bulbs work great when spread around the room but not so good when all grouped together. Look at hot countries where CFL were used well before here with more temperate climate and you will often see 9 lights per room split between two switches 3 on one and 6 on the other giving as a result three levels of lighting.
However to convert out homes needs some re-wiring and that in turn means re-decoration most don't want to do this just to save a few pounds. Florescent lamps are hard to work out as the tube coating and the control gear means one 32W florescent can produce double the output of another 32W florescent so figures as to which are best florescent or LED can be confusing. However in last few days got some new LED lamps and I have to admit compared with CFL around double the light output. But the 22W florescent at the top of my stairs with emergency back-up using HF ballast would need a whole array of LED lights to replace it and is a really good unit. Been up for well over 20 years and replace the orignal second hand tube last year.
However the 8W CFL I fitted 18 in dinning and living room 3 years ago have only 9 of the orignal lamps left and are now far dimmer then when fitted so the 1.4W LED fitted this week is as bright as the CFL. If Lidi do them again I'll be there in a flash and replace the lot.
Fitted a electronic 2D in my mothers kitchen mainly as no earth and needed a double insulated fitting and at 22W reasonable high ceiling a single light is fine. however would not want to fit in living room may do the job but looks too clinical.
I am sure they do but not noticed LED lamps getting dimmer with age. However with any florescent that is a problem and they do get dimmer and dimmer with age.
Early LED I tried were failures but have to admit now it's a very different story but at £900 you are looking at a lot of work and I question if retaining 50mm spot lights is really cost effective. I would want to look at all options first.
