Problem Paint!

We have a T Reg 99 Seicento which seems to have had some body work done by the previous owner which included a new passenger door skin. The bodyshop must have been abit shady cos they've tried to blend the paint on the bonnet and have left a slightly darker strip on it (only really visable close up/in the sunslight) and also the paint has sort of left an area of cracked finish, where apparently old paint and new paint have clashed...TCut did do a slight improvement but dont know what else to try cos the polish has left it looking bad again (used Mer polish) also I've just noticed some little pin head dints in the paint which I;m sure have only just appeared.

Just want to have the bodywork looking good without too much expense but dont know where to start! Any ideas?

Sounds like the bonnet needs sanding down and repainting..
If the paint starts to react, it isnt going to make itself better, it'll just stay cracked, or possibly even crack a lot more..

The same happened to my car when I crashed it - they repainted the bonnet with a lot of green in the paint for some reason so now after I've done my badboy brows and painted them myself you can see the line of green across the middle.. Luckily for me I have a mate who is going to put my vents in for me and respray the lot for a few cans of lager!