The legal minimum tyre tread depth in the UK is 1.6 millimetres, this should be across the centre 75% of the tread around the complete circumference of the tyre.
Your vehicle handbook will have the details of the correct tyre size. Alternatively, you can check the side wall of your current tyres. They will usually be in a similar format to this:
You can get an MOT up to 28 days before it runs out and keep the same renewal date. If you do this, your new MOT expiry date will stay the same, so you are then covered for up to 13 months, if [...]