It's not an offence to drive without a spare tyre in the UK.
However, many people will recommended that you have one if possible. If you experience a puncture or other tyre malfunction, having a spare can help get you back on the move much faster.
Having a spare wheel with you also means that you are likely to be able to repair the problem yourself instead of having to call out a breakdown service or arrange for another vehicle to come and collect you.
So, although it's not mandatory, it's advisable for drivers to carry a spare wheel with them when travelling long distances or in remote locations.