Hey no probs.
Suppose it depends how old the lambs are. It they'll be around eight or nine weeks old come the end of May then you should be fine to do it.
Bluetongue - just asked the other half about that, he doesn't think they need done, unless you're in the South East -ish Kent or East Anglia waywhere the midges can get blown over from Europe. We don't bother with ours - the only time we did was when there was the confirmed breakout a few years ago, and that was because we were told to, rather than because we were at risk..