XBOX One beeps 3 times but wont turn on.

When you say a UK power supply do you mean an official power adapter for the console or is it just a power converter for the region?

If it's a power converter perhaps the issue lies in the fact the console may not be getting enough power.

If you don't have a power adapter from the UK you should try contacting
phone support. I can't confirm whether this is true or not but have heard some people online say that they can get a new adapter if the console was bought in a different region.

it wil beep a few times over about 3-5 minutes but only ever one beep. The it will power off. Also beep a few times then turn on.

I have cleaned all buttons, last night i could not play at all it would turn off after 3-5 mins

The first condition is a common phenomenon and probably your Xbox One is in power state. The second condition is terrible and you may need to repair or even replace the Xbox One.

You are able to power cycle your Xbox, tap the eject button repeatedly, check your power cable, or unplug your Xbox for 10 seconds to fix the Xbox One not turning on issue when it beeps. Click here to
get the specific steps.

Yes Faithless, I did but it doesn't take me my issue where my console wont turn on, just blank screens. Anyhow, I tried holding the power button and eject at the same time and my console still wont turn on. Just a beep, flashing xbox sign, then nothing.
I guess I'll just exchange it.

Yes i just hear the sound of the Xbox one when it turns on it ''beeps'' then after it ''beeps'' again and turn off. I was playing lately today on it, and it just ''beeps' turn off while i was playing....

still any solution?