Hello mate.
There are many different masks on the market. I would avoid the very cheap ebay ones.
A lot of people rate Speedglass masks. Personally i dont, easy to forget to switch them on, and not that much neck protection.
Theres not that much difference in the specs, but things like fixed or variable shade will dramatically change the prices. Also not so sure on the life of a cheap cartridge.
Another thing to remember is the availability of replacement front and inside cover lenses. How easy would it be to buy lenses for a chinese unbranded one from ebay!!??
I have used a Nederman/Esab for years. My current one (with fresh air pack) for about 5 years now. (Thats everyday, heavy duty use) They are available in various options from about £90 to ££££! And lenses are easy to come by. Solar powered, so no batteries or switches...another reason for me to choose these is the available accesories, ear defenders, hardhats, fresh air packs, face seals that can be fitted. Not relevant to your choice i doubt!
I would without doubt reccomend one to you,
http://www.migtigarc.co.uk/Auto_Helmets ... auto_.html
The 10/11 would be ideal.
If you wanted a cheaper option, these, made by parweld are reasonable.
They have niggles, like not a proper seal around the froint cover lense so dirt/ dust can get down onto the lense. But to be honest, if you look after it...and its not going to get heavy duty use...
http://www.rapidwelding.co.uk/633487