I am thinking about buying a giant yukon are they any good?

The Yukon FXs are a bit like a budget Maestro bike. The suspension lack some linkages, so they don't ride as well, but for the money they're alright. You must be looking at old stock or second hand as the bike is now discontinued. Avoid the FX3 with mechanical discs and really cheap SRAM stuff. The FX2 is better, with the hydraulic discs, but the gearset is still an obvious cost cutting exersise and the first thing you'll need to upgrade.

real cheap 2009 models to be had here.. check to see if they have the frame that best fits your size..
http://www.paulscycles.co.uk/products.php?plid=m1b4s1p0&tbv=GIANT_Mountain_Bikes_Full_Suspension

I bought a Giant Reign X0 2008 model at a fraction of the retail price from pauls, bike is brilliant and the customer service is good..

My Brother in law bought an FX2 from Pauls. No problems with it, came with a shock pump that I wouldn't have expected at this price. Pedals too, not great ones but ideal if you want the 'buy it and ride it' experience. Took it round Cwmcarn last week without any incident.

If you're willing to spend a little more, buying ther FX1 is a better bet though – for £100 more you get a 27 speed deore groupset instead of the 24 speed alivio, and the fork is a Rockshox Tora instead of the Dart. These would cost you a lot more than the initial price hike to upgrade. You don't get pedals though, so worth factoring this in.

Alternatively for similar money you could look at the classifieds on the forum. You get a lot more bike for your money when buying second hand, just make sure the seller's got decent forum history, not just a 'joined up to sell' type.

Thanks everybody I was looking at paulscycles website the prices are really good but I think at 6'3 I probably need an xl which they dont have so will have to look at alternatives

I have the FX2 as in my opinion it was the best bike for my budget. I got it early last year.

Its a great bike and I'm really happy. It weighs quite a bit more than those of my mates but they have much more expensive kit. I agree with the comment about going for the FX1. I've since upgraded the fork from dart2 to Tora air and its loads better. The dart2 is really stiff even for a heavy rider and therefore has only 50mm usable travel max. The rear shock is fine although I find I put much less air in than advised. Not sure about the linkages – it just works.

The brakes are good and 24 gears is fine. I honestly think I got a bargain and I'm very pleased. Its taken a fair bit of heavy riding round Afan a few times as well as plenty of south England rides. If you find one in your size I'm sure you'd be happy.