Series two's last episode of the sitcom, which featured Tanya and Clive's second wedding, logged 742k (4.1%) - a turnaround from a fortnight ago.
Despite growing in critical acclaim, this year's run has been less popular on TV than its first series in 2010, compounding rumours that the BBC may not commission a third.
The Chelsea Flower Show (1.73m/8.7%) and The Fish Market: Inside Billingsgate (2.21m/10.5%) preceded Grandma's House on BBC Two.
Elsewhere, Long Lost Family's penultimate edition dipped to 3.96m (19.5%) on ITV1 at 9pm, but added 275k on +1. The Davina McCall/Nicky Campbell series, which had been solid before last night, was not helped by a lower-than-usual lead-in from Coronation Street.
Hot weather also seemed to affect BBC One, which could only muster 2.91m (14.6%) for Planet Earth Live in the 8pm hour, and 2.08m (10.2%) for a Diamond Jubilee special of National Treasures an hour later.
Meanwhile, The True Story (656k/3.4%) and Cowboy Builders (670k/3.3%) were low scoring for Channel 5 between 8pm and 10pm.
Overall, ITV1 led primetime with 21.9% (+1: 0.9%), comfortably beating BBC One which had 17.7%. BBC Two claimed third place with 7.6%, ahead of Channel 4's 6.6% (+1: 1%), and Channel 5's 3.3% (+1: 0.1%).
> Read today's multichannel ratings for Thursday here
BARB ratings data supplied by Attentional