Free Traffic Legal Advice

You parked in a marked parking bay with a sign on the wall saying 8am to 8pm pay at machine, display ticket with an arrow pointing to where the machine is located. This is all visible in the photos you have posted. The ticket machine is just round the corner : -
https://maps.app.goo.gl/78KPHge5hYGBiRRd8

The other, yellow, sign applies to the yellow line on the carriageway. Are you a visitor to the UK, and therefore unfamiliar with UK parking arrangements ?

As it is a hire car, you can only submit informal representations against the PCN. If they reject these and the PCN remains unpaid, a Notice to Owner is sent to the owner of the vehicle, and this will be the hire company. So you need to check with the hire company what their arrangements are for PCNs received by drivers of their vehicles. A lot of them just pay the penalty, and off-charge, plus (naturally !!) an admin fee.

No I'm not a visitor to the UK. I've parked here several times and was unaware that each area of signage relates to seperate areas. They are both very close to each other and don't seem make it clear between each parking area. I've never (maybe luckily) had a ticket when parking there.

Is there any basis to appeal this?

None that I can see based on the contravention itself. However, councils must obey the law and regulations on parking same as you, so there could be a 'technical' appeal based on their mismanagement of the enforcement process, but I can't see one.

If you've parked there several times without any PCN it is probably because outside London, CEO patrols can be quite spaced-out, so you missed a CEO patrol. In london, CEOs patrol the streets 24x7. All penalty money is kept by the councils, less any adjudication fees.

First off, sorry to say it, but I seriously suggest you "mug up" on road markings and signs or you'll get a lot more PCNs !