I would go for the 200mbps package at least.
But why? For the vast majority of people that would just be a waste of £15 a month.
Indeed. If you have no justification readily available for additional speed and need to ask others to justify it for you, this indicates you do not currently have an application for the higher speed.
I've got 80/20 FTTC that synchronises at maximum speed. The reason for choosing 80/20 is that the additional upload bandwidth over 40/10 is sometimes very useful, also the additional monthly cost on my ISP is a modest £3.
Most of the time the entire network here could operate perfectly happily on a 40/10 connection.