I realised I made a mistake above as I was basing the Mount Panorama times on using Racing Hard tyres not softs. A few laps practice tonight and I was in the 2:04's though 2:03's is definitely possible so I'd anything under 2:06 is fast being there's so many chances to make mistakes over the mountain so really anything under 2:10 is doing well.
As for Tsukuba, it looks like my guess was right about the TT. I only did 2 or 3 laps in a few cars but the TT was easily the fastest though the McLaren was pretty close - more testing is required. Though on to times; 56 second lap is possible, maybe 55's but I haven't done enough laps to figure it out, but really I think a good time to aim for is anything under 1 minute.