mono-stereo
This. Can’t overstate how helpful a meat probe is… I’ve used this one for the past few years, and is the best I’ve used.
https://buythermopro.com/product/thermopro-tp27-long-range-wireless-meat-smoker-thermometer/
Their stuff is available on Amazon in the UK.
One note - if you’re looking for a final internal temperature (say 55C for medium rare), remember to take the beef out when it hits 50-51C, as it’ll continue to cook while it rests. Oh yeah - and make sure you rest it for at least ½ hour for a 2kg piece of sirloin…