I was wondering how much time to allow for travel from town of Oxford to St. Pancras for a mid June Eurostar train to Paris at 11:30 am? Should I buy rail tickets two months in advance online on national rail to depart Oxford and head back to Paddington and then tube to St Pancras or just buy tickets at Oxford station when ready to leave there on the actual day of travel? Thanks for any suggestions. We've already booked Eurostar so can't change that part.
I suggest that you take a train that arrives at Paddington no later than 10:00. That will give you enough time to get to St Pancras International to meet the 30-minute check-in deadline for the Eurostar.
If you had booked a through ticket with Eurostar, they would have put you on the 9:31 with a 61 minute connection from Paddington to St Pancras. This would be tight but you would have been put on the next service if late. You can buy a ticket from Oxford to London International (CIV) that has the same protection, and includes the transfer, and protection against delay. Or you can buy a regular Oxford to London Paddington ticket and take the transfer risk and inter-station transfer costs. Adding an hour on may be a reasonable precaution, but no guarantee of course. Booking in advance is probably advisable as this is peak time. Only some of the trains from Oxford have reserve-able seats though.
www.seat61.com has strategies for buying English train connections for the Eurostar.
Thanks for all the helpful suggestions. I'll check into the CIV type tickets and make sure we have ample time to make the connection.