We tend to do our journeys to the UK like this:
Leave at 16:00 when school finishes. Stay overnight in budget hotel in St Quentin.
Get a breakfast ferry the next day and head up to Peterborough or Bath for lunchtime.
St Quentin is good because it is close enough (<90 minutes) from Calais to time the arrival time very accurately.
On the return journey we always get up early. Get a breakfast ferry again and get back to Zürich in one day.
We tend to stay in the
B&B credit card motels which have rooms for 4 people. The rooms are pretty spacious compared to Premiere Classe. They have hotels in St Quentin and Calais.
On the ferry we always go with P&O so we can use the Langans restaurant which is great for breakfast and never busy.