Advance train tickets advisable for Windsor-Eton to Paddington Station?

The ticket is an anytime day single, just purchase day of.

advance train tickets are not the same as tickets bought in advance. The former are a type of ticket which has to be bought in advance, comes with quota based discounts dependiing on how quick you were, but also comes with fixed itinery and very limited (if any) flexiblity or refund options. They aren't normally available for this journey. But almost any type of ticket can be bought in advance - this means you hand over your money early for a ticket which could be bought just before departure, in return for not having to do it when rushing for the train, but risking the new refund conditions.

And the question you should have asked might have been, what's the cheapest fare? Because in this case, if this is a one way journey and each passenger has a seperate card/phone which can be used for contactless payment the cheapest fare doesn't even have a ticket and can't be bought in advance, you just touch in at the platform scanner at Windsor and touch out at Paddington.

https://www.gwr.com/your-tickets/smart-tickets/contactless-payments

during the commuter peak this will be £1 cheaper than the Anytime single ticket but once the peak is over it becomes over £5 cheaper!

Sorry for my lack of clarity - It would be a one-way ticket and yes we would prefer the cheapest/fastest public transport option.

me.crewe gave you the answer. Contactless from Windsor & Eton Central to Paddington. No ticket needed.

For schedules use either GWR's website or the National Rail website.

we would prefer the cheapest/fastest public transport option.

Those are mutually exclusive words, especially if travelling beyond Paddington. The cheapest (but the longest journey time) is the Green Line bus at £3- it runs to London Victoria.

Even if you add on a £3 tube fare from Hammersmith to Paddington it is still the cheapest- https://passenger-line-assets.s3.eu-west-1.amazonaws.com/readingbuses/RBUS/702-timetable-20260328-de010614.pdf

Thank you everyone for the information.