Which bike for a week of moderate cycling around the Netherlands?

I'm looking for a bike for a week-long cycling holiday to the Netherlands, expecting to do ~5 hours of cycling per day. However, I've never been on such a trip, so coming to the bike buying process very naive.

My understanding is that the bike routes I'll be following in the Netherlands are mostly paved, and I myself am 6'3". I think that means I should be looking for a road bike with a XL frame, but would like a second opinion on that.

I'd like to buy something second hand, ideally between £100 and £300.

So far I've found appropriately priced second hand items such as this on eBay – am I right in looking at bikes like this? For an extended cycling holiday, would I need something with a softer saddle?