One of the problems when you start out, or as in your case- restart, is the cost of eqipment, and whether it is suitable for what you want. Ok so you bought a GT from Halfords. Not my favourite store, or my favourite bike, But at least you are back riding. Now the problem is to get a bike that is suitable for the type of riding you want to do. One Point I would raise is Cost. What you are looking at in the full suspension style of bike is going to cost you a lot. You should find a local Bike shop, and see what they can do about trading yours in for the bike you want, or even look at Secondhand.
Failing that, persevere with the aggressor until your skills and knowledge come up to par, and just keep riding.Then in a year or so's time you WILL know what bike you want, you will have had your moneys worth out of the GT, and you will have regained the skills you lost through giving up riding for all those years.