Ok, it seems like the adjustable stem doesn't come on the UK version of the bike but the riding position still looks more upright than the bikes previously posted here. You should try some out and find out what kind of riding position you like before you buy anything.

The bikes above have riding positions that are more upright than a road bike, but I could see leaning forward like on a mountain bike could be undesired also.

The Giant Seek is more upright than the Rapid. The Rapid is more road bike like and the Seek isn't far behind. What type of road riding are you doing? Is it urban streets where you'll stop frequently or are you going long distances without stopping. More mountain bike like would be the Giant Roam which has bigger tires for more comfort and better off-roading. Even more upright would be something like the Giant Cypress.

The Marin Novato is a hybrid more mountain like. Riding position is probably close to the Giant Roam, but with smaller wheels and fatter tires which result in a cushier ride. The smaller wheels would lower gear ratios (an smaller moment of inertia) so you might accelerate slightly faster or pedal more strokes with lower effort to go a shorter distance compared to all the previously mentioned bikes with 700c tires. Top speed will be lower, but somehow I doubt you'll reach 30+ MPH on a regular basis that shouldn't be an issue.

Marin, Giant, Jamis, and Kona are all decent bikes made by reputable companies. Within the same price range, the bikes will generally be about the same; differences should be minor component wise. However the way the ride, feel, handle may differ.

It's highly suggested that you don't order a bike for delivery since you're not sure what you want. Go to a few bike shops and try some out so you can get the different feel of each bike and then choose the proper frame size. These are paramount to your enjoyment of your bicycle regardless of what you end up buying.