Deffo disrespectful. OP has said she doesn't like it but he persists. That's unacceptable. And the tissue is gross, what is he, a teenager?
But OP, you say 'Quite honestly it makes me feel sick. I am no prude and don’t have a problem with him doing it, just not while I’m sleeping next to him.'
This sounds a bit contradictory tbh. No prude, no problem, but you feel sick? This might be a language thing; are you using 'sick' to describe your anger at his ignoring your feelings on this? Or do you really mean, you're repelled by it and it turns your stomach? In which case, maybe you do have a problem with it? How would you feel if he masturbated, say, at bedtime? Say, you'd both gone to bed, he felt sexual but you didn't & so he asked (the asking is so important) if you'd be ok with him sorting himself out? And tidying up after, obvs.
I'm trying to get at whether it's the physical act in itself that's the problem or the lack of respect. Because, as other posters have suggested, just because he's wanking, that doesn't mean it's not a sexual act between you. You're there in the room, awake, woken up by it. You can't be neutral, uninvolved. At the very least, you're forced either to indicate in some way that you're ok with it (eg watching, or at least appearing unconcerned) or to indicate in some way that you're not (eg annoyed face, turning away).
It's impossible to be awake and be neutral, but by carrying on wanking, knowing you're awake, he's demanding that. In effect, he's saying, can you just erase yourself until I come. Is that what is pissing you off? Or is it more the physicality of the act? I ask because if it's the former, I guess there's at least the possibility of making him realise that he's putting you in a really unfair position - one which is bound to have repercussions on the consensual side of your sex life. Bring back the consent, and you may find a solution. But if it's the latter - or he carries on trampling on your feelings, then there's no chance.