Advice please best time to book a cruise for October November this year .....

About 4 to 8 weeks before sailing many cruise companies panic sell and reduce prices , MSC are one of the lines that does this. Not sure about the number of days you want to cruise for but you have to go with what the cruise schedule is far. Nothing stopping you choosing a cruise(s) now and waiting to see if the price drops . You could also sign up for emails from cruise travel agents ( iglu, Cruise club, etc. , Just google book cruises uk and loads will come up). If you do want to book with MSC , never book direct with them as customer service is poor but luckily service on board is good.
You also need to decide where you want to sail from, Southampton has the most choice or you could fly cruise.
Start by looking on here to see if anything takes your fancy - cruise.co.uk/ (edited)