Leon,
Personally, I'd avoid a .410. Try a 20 bore if you find a 12 bore too much right now. I know they have their friends, but I think a .410 is a rat gun. They are okay for really close vermin work, but, to be honest, given what you have said about your uncles shoot, I don't think its suitable (its not a gun for a high pheasant). A lot of guys shoot 20 bore although I would say a good 12 bore is a lifelong investement
The money you are talking about is going to buy you a basic (very basic) second hand gun so don't worry about makes. You need to decide if you want to game shoot or clay shoot or both as the barrel length, chokes etc can be different.
I suspect you will use clays to practice live quarry so get a game gun - say..1/4 and IC choke/ I'd hope for an over & under but settle for a side by side.
Shoot a few first and find out what works. I suggest get a few clay lessons first and use a club gun as ArkAngel said
Oh..BTW ArkAngel ...I was (really) shooting a Baker Rifle last month...and....?
Red