Be careful and be prepared to waste money when you buy from these guys, treat it like a crapshoot. I made 4 separate orders over a few weeks, each order arrived with either clearly defective lenses, lenses that made me dizzy (but unable to prove the fault, unless I had a laser measurement) or warped lenses due to being put on too tightly by lazy optical staff. This was a nightmare, tried to get some refunded or replaced and spent close to 1 hour with online chat going around in circles, gave up and cut my losses. The optical centre was way off, the vertical alignment was different on each lens - indicating that staff did not quality check the lenses or didn't really care.
If you have a laser measurement device that can verify what you receive from Goggles4u then you could complain, otherwise you're in for a heck of a time trying to explain that the glasses just don't feel right or make you dizzy.
Save your money and time and go with a more reputable online dispenser that can provide you with a laser measurement of the finished lenses, these guys are just low, low quality.
Also, they use CR39 plastic for the free lenses, which have great anti-reflective properties, but they use Apsheric shaped lenses, which are cheaply made and give you headaches. I'd recommend a shop that gives you more comfortable Spherical lenses.
If you ever decide to get tinting, you can't, repeat can't, get anti-reflective coating on the lenses, so they end up with so much glare they're impossible to use.