Even if it had been purchased online and delivered, I'm fairly sure that the Distant Selling Regulations state that the item must be returned in 'as new' condition, i.e. unopened.

I think if you take it back to Currys and explain your concerns, they'll be happy to exchange it for you, even if not legally obligated to do so. Their aftersales service is fairly decent in this area in my limited experience.

...sometimes the default 'picture quality' setting is fixed at mid-value. Perhaps, you might be able to reset that value to a higher picture resolution, via the MENU.

Comets returns policy from their website:

"For click and collect, call & collect and store purchases that are brand new and still sealed in the box - bring it back with your receipt within 28 days of purchase. During the first 14 days we'll exchange or refund the item if it's unopened. After the 14th day, if the item is unopened, we'll exchange or put the value of the returned item onto a Comet gift card.

Sorry, we can't accept any products that have been opened, or returned with missing parts: remote controls, instructions etc."

I would definately go back to the store and ask for some assistance. They have some very good expert staff on the camera section. Make sure you find one and ask them what they think.