Whilst I appreciate that you are looking to get glasses at a much lower price than you've been paying before. I would, personally, think twice about ordering glasses from an online manufacturer. Whilst the specs are cheaper, they are also from 2 or 3 seasons previous, which is why they are so cheap. Secondly, you can't guarantee the quality of your lenses, nor can you guarantee they will come from a reputable company (Jai Kudo, Essilor, American Optical et al), this could have serious repercussions in terms of coatings etc. Thirdly, the manufacturer relies on the measurements that YOU take, and in the case of high index lenses that you would require for your prescription, if the measurements aren't exact this can lead to vision problems. Lastly, if anything were to happen to your spectacles and they needed repairing, most opticians now will charge you for the repair, which can run from 50p for a new eye wire screw to ££'s for replacement lenses if needed.
Whilst it looks like a good idea initially, costs can spiral and you could end up spending as much as you were originally looking to save in the first place. The reason that opticians are expensive is because you are paying for the service and aftercare. They will take the correct measurements. They will align the glasses so that they are fitting correctly and they will also solve any problems that arise later on free of charge.
My personal experience of online manufacturers is not very good unfortunately, having worked in numerous opticians over the years and seeing the "high quality" that they guarantee.
My advice to you is be prepared to pay that little bit extra if you want to have better quality specs that are going to last you longer than 6 months!