At only 5 hours, the LEC CF250L has a fairly short storage time during power failure compared to most of the other chest freezers that have been available for a comparable time to this freezer. The storage time during power failures of similar spec freezers that were released around the same time as this freezer range from 5h to 90h.
There are a number of alternative 5h storage time during power failure freezers currently available which you might want to look at including the CF200L (£169), or the CF150L (£159.99) both from LEC which and both of have better reviews.
Freezers with a longer storage time during power failure that might be worth looking at include the Beko CF374 (£158.99) (30h and higher rated).
What does "storage time during power failure" mean?