In answer to your questions, Richard G4YTV was at his home location (IO93UU82FR) using his 9el M2 beam at 20m AGL. He uses a MVV144VOX 2m Masthead Preamplifier feeding a BATC Minitioune v2 DATV receiver.
There is no restriction against using any digital mode in the UK licence on the 144 to 146MHz segment, so we could run 400w to any antenna. What it does say is that the bandwidth of the transmission should be the minimum appropriate for the modulation method in use. I don't think there could be any argument about that when using 125kS/s! With only 2MHz available in Region 1 to use, it would be unsociable to use more spectrum.
The UK only segment of 146 to 147MHz requires a permit, known here as a Notice of Variation (NoV), but the application is very easy to do online via the RSGB website. The NOV restricts the power to 50w ERP and there are certain geographical restrictions too. However, its possible to fit 500kS/s into that band without upsetting other users or exceeding the band edges.
Welcome to the forum.
Thank you for the additional info on the station in Dordrecht. I'll include that in my Activity column in the next CQ-TV issue. You are very well equipped for 2m so it might be worth trying the path across the North Sea to Groningen; it's about 450km although the flight paths are not so well aligned for AS it would be worth trying.
Unfortunately, Richard and I didn't see your post about PE1ITR until Saturday so we missed that opportunity. That's a shame because the path from Texel is just under 350km and might be a little easier. I'll contact you via PM and send you Richard's and my mobile phone numbers so that you could alert us with a text if there is another activation.