If it'd been a choice between having the extra room by adding the conservatory or having nice smooth paintable walls, I'd have gone short on space!!!
I have enough trouble trying to get a border straight and there's usually blood, sweat and tears over that because I'm too much the perfectionist to accept that perhaps the walls just aren't straight and the damn thing won't look 100%. Whenever I decorate other people scarper, not wanting to be the one to light the very short fuse that emerges with the task. Wallpapering for me would just be a living hell!
At that price, I should hope it flippin well IS nice! It'd be a real sod if you'd paid that and then one of you decided that actually that £3.99 roll would've looked better after all. Glad it's going well anyway. Out of interest, did you hang the paper yourself?