I did the reverse of this trip last summer, starting in LIS and heading to LHR before heading back to Canada.
The Qantas Lounge is a great space in Heathrow. It's probably among my favourite piaces to "hang out in". Unfortunately, I don't like the lack of available light there and I find the whole experience quite dark, if not uncrowded. It's always empty whenever I go through there. After a drink or two, it's always over to the Cathay Lounge for me for some nibbles.
The ANA lounge looks far better than the Tap Premium Lounge in LIS. I didn't particularly care for the green color of the TAP Lounge and it was pretty pedestrian when we went through.
Otherwise, I really enjoyed LIS as a place to visit and we hope to get back there some day soon.