Buy from anywhere but BB4L / JBBG etc! well that and Special Airsoft Supplies
Some good shops are Zero One, Airsoft World, Land Warrior Airsoft, Airsoft Zone and Fire Support
Pro Airsoft Supplies and Wolf Armouries which are in London
I have seen that gun at TaiwanGun, which is a Polish retailer, so they don't do two-tone.
Pretty sure I saw the MB4411 at Patrol Base the last time I went but it isn't actually listed on their website.
If you can find it most places will do a two tone painting service for £10+ or some like Zero One will do it for free.
I wouldn't recommend a sniper rifle as a first gun though. Sniping in airsoft is not as fun as it might look because you will realistically only get a few kills.
Not only this but building a ghillie suit is basically a must if you want to stay hidden which is gonna take a lot of time and work.
Also the most important thing is sniper rifles take A LOT of upgrading to be any good and it costs a lot. When you buy one stock the range and accuracy won't be great so you might as well just have an AEG.
If you did buy a sniper rifle I would say buy a Tokyo Marui but they are gonna be around £200.
Welcome to the forum by the way