If I could only get a straight pull AR I wouldn't bother, it sort of defeats the point really, and all you have is an expensive "pretend" AR15.
If you can't get Military style semi-autos, then there are other semi-autos they will do the job fine, which is what I'd go for if that was my options.
But like I said we can get a normal AR but it has to have a 7 round for it to come under our basic gun licence. They are probably 1.5 times as much as a bolt action but you can get new uppers relatively cheap.
I'm kind of glad that you have to get a different licence to be able to have full military configuration ARs as there are some gun owners out there who I wouldn't trust with an air rifle to be hunting with.