Anecdotally, I had no problem being in the US for a week, back home for about ten days, then in the US again for another 2.5 weeks (also a British citizen travelling on VWP).
I can't see you having a problem, either. Like mine, your two trips wouldn't come anywhere close to the 90-day limit even if you decided not to leave the US for those three days. That would give a 31-day trip. You're obviously not trying to game the system by going home for three days.
The only reason the 90-day limit might become relevant is in the future. There's a rule of thumb that you shouldn't be in the US on VWP for more than 90 days in any 180-day period. If you were to make a hypothetical third trip to the US that was very long, you might have problems if those three days you spent at home turned out to be necessary to keep you under 90 days in some 180-day period. In that case, it would look like you were trying to game the system. However, that would be a problem on this hypothetical third trip – it shouldn't be an issue for the trips you're actually trying to make.