What do you need to ride one of these things? A provisional? Seems like cheap transport for just a to b.
CBT will allow you to ride upto 125cc bikes.
If you've got a car licence and passed before Feb 2001 (I haven't got an exact date), you can just hop on a <
50cc moped. Though doing the CBT is recommended.
If you got your car licence after Feb 2001 you'll have to do the CBT anyway. However, the category P provision will then will last the life of your car licence for (you'll still have to retake every 2 years to ride 51-125cc bikes or sit the full licence). You can also take the CBT then pass your car licence and retain the category P provision.