I'd stick with the MP5 myself. Everyone and their dog has an M4 - it gets really tedious...
If you get the
G&G MP5 from Zero One, they will two tone it for free and also give you a free voucher for £20 off a day skirmishing.
Their rep for customer service is up and down, but so far they've been very helpful to me and I'd have no worries about buying a gun from them.
BTW, if you want a two tone because you are u18, once you have been airsofting a few times, and can prove that you have (get a receipt say), or become a member of a site, you can legally "Manufacture a Realistic Imitation Firearm", ie take the bright paint off (with Fairy Power Spray

search this forum or yt). But if you buy that SRC (which is also a good gun btw, but don't be swayed by 'full metal' - even a real MP5 has a fair bit of polymer on it), the orange isn't paint, the plastic is that colour and painting it is rarely that successful.
Also the customer service on that site is notoriously terrible. As Mike said, avoid any site with bbguns in the url - they are all variants of the same eshop site template and all have an inventory which is mainly utter shight about which they make outrageous exaggerated claims, or go further into outright lies (such as calling that SRC MP5 full metal). If you have any kind of problem with them, you'll have to really make a nuisance of yourself to get it sorted, and they're such a cowboy operation that they do supply more guns with problems than is typical - refund? Ha! As of now I don't know if they are all linked in any other way than using the same website template, but I do remember a fair while ago finding airsoft ebusinesses for sale on ebay, so they may well all be the retail fronts of a single supplier, each nominally owned and 'run' by a different pretty disinterested person...