For £50.00 you are spoilt for choice! I can't recommend a particular model for you, but here are some of the things to think about before deciding.....
Like so many modern electronic devices, even the cheapest ones probably have more functions than you will want to use.
I think all computers will record total mileage, and trip mileage which you can reset between each journey.
Most computers will display average speed, some calculate the average using overall time, others discount the time when your bike is stationary outside the cafe half way through your journey.
Another point to consider, do you want wireless or wired? Wireless employs a radio signal to send data from the detector on your front fork to the display unit. This necessitates a battery in the detector unit as well as a battery in the display unit. Wired uses a cable to transmit the data.
Display units are usually removable for security purposes, of course if you don't remove it when leaving the bike unattended someone else might.
More advanced models may include an actual time (clock) display and some have cadence (the rpm of your pedals) displays.
Lidl often have cheapo computers for a lot less than £50, but bike shops should be able to help you make an informed choice for a little more expenditure.
