Managing leaving in the most cost efficient way

[#1]

My current ADSL deal ends on October 20th,which is a Friday and subject to comparing any haggled PlusNet deal with Sky's offer, I may be moving to Sky.

As PlusNet say that they don't do migrations at weekends ,I assume that if I give Sky the go ahead this Friday(and assuming the average 14 days or 10 working days) then Sky will take over on 23rd meaning paying PlusNet  at full price for Saturday,Sunday and Monday.

However, if I contact Sky tomorrow, they make take over on the 20th or even 19th( ie on the last day or on the penultimate day) ,so what penalty would be incurred in these two instances?

I don't think amounts are huge in the latter cases, but which would be the best route to take, as you can't tell a provider what day you would like the migration to be ?

[#2]

Since migrations are gaining provider led, if you are planning to move away from Plusnet why not contact your new provider and tell them when you want the new service to begin? Your new provider will have to negotiate necessary work in the exchange with Openreach.