My advice would be to find a local club where you will shoot - and go and socialise and with luck you will be able to try a few guns, see what the locals use, learn about gun fit, master eye etc - and I've no doubt you will get LOTS of opinions. Some clubs have either a resident (or honorary) coach who may be able to help. Maybe take a few lessons. Find out which local dealers are well rated and respected by the club members. Club members in the UK are usually a sociable lot and keen to help.
Then, armed with that, go to the recommended gun dealers with a budget in mind - and see what they have to offer in your price range. Don't rule out second hand as guns don't usually 'wear out' if you stick to the better known and respected names such as Beretta, Browing, Miroku etc. MAKE SURE that you get a gun that fits you - a good dealer will be honest and helpful over this, but its quite hard to get just right with a beginner whose gun mounting is not consistent and developed. Here some dealers either have a pattern plate - or access to a clays ground and will give a trial to serious buyers. Such dealers are worth seeking out for a beginner in my view.
If you go for an unknown name, you will (a) have more trouble reselling when you come to upgrade, and (b) have more trouble getting repairs should you have any problem. I would personally prefer a used 'known name' over a new 'low grade' and stick to the popular names (they got popular by being good).
Most likely gun would be an over/under, 28" or 30" barrels, single trigger with multi chokes. If you go fixed choke, and want to shoot skeet and sporting I wouldn't go for more than say 1/4 choke in either barrel. In the UK, 12 bore would be the most plentiful.
Having said all that, I'm in a minority - and shoot a side by side at clays much of the time - and if you want to do that, the Spanish guns from AyA, etc can be very good value and are sound guns.
