I get wee'd off if a bird craps on my car, let alone finding damage by some brain dead scrote. My general rule of thumb: If you can feel a scratch with your fingernail, normally it won't polish out.
The bumper clearly needs to be repaired. It will require a good sanding down and flexible plastic filler to repair the hole. If is was just this scratch then it's in a nice place to paint without having to blend into the rear quarter panel, but you have the scratch on your door as well. Where is the scratch on your rear door? Towards the middle, front or back? If it's in the middle you MIGHT get lucky, but if it's more towards the front or the rear then it will need blended in to the nearest panel. If it's towards the rear of the door then it will be a paint job on the door, part of the rear quarter and the bumper to keep the colour matching because silver is one of the worse colours to get right.
To me the scratch on the door looks too deep to buff out. You can see what ever has hit it, it's hit it gently to start with then towards the middle it's gotten a bit harder and made more of a rough gouge (rough edges and tiny chips) than a scratch. It will also need painted. If the scratch is towards the front of the door it will need blended into the front door and the rear bumper will be painted on it's own. You will just have to see what the painter offers to do.
If I were in your shoes I would just leave it and look to get it sorted out come selling time. You will get more damage, there's no doubt about that. BUT...if you did want to get it painted I would go to a proper bodyshop. That way you know it's done right in the proper painting conditions, like the correct curing times for the paint, clean environment, baked on paint in a booth etc. Mobile repairers are alright for small repairs, but there's nothing worse than getting dust and crud in clean paint work that will later need to be sanded down and polished out, or even having to get the job done again because the correct painting conditions were not met.
The only problem with going to a body shop is the price. If the door needs blending into the neighboring panel, along with the bumper repair you're talking about £400-700, depending one the bodyshops prices. Bodyshop prices are worse than dentists and vets, nice for us body people but not for the customer. Now if you lived near me I would do the job simply for the price of the materials used, I'm just that sorta guy

unless you're a knob, then I will require beer as well

.
My friends and others I know prefer coming to me when they need painting or body work done. I do favors for them and they do them for me, that's just how things work. I have friends in many places so it's handy when I need mechanical stuff to my car or other jobs doing. I can't remember the last time I paid for parts or an MOT. You car would take me one day to sort out and be able to drive it away. A bodyshop will have it for a good few days.