London-Glasgow takes about 4h45m typically with about 7 stops. There's a train every hour between from 5am until about 6pm. Today the 5:30pm train is full, the 6:30 is £119 (€140) for a single ticket 2nd class. If you are more than 6'2" tall your knees will be wedged against the seat in front of you like on a budget airline, the ride quality on the train is too bumpy to be able to use a mouse or trackpad accurately with a laptop, you will struggle to select paragraphs of text. There is not really enough room to use a laptop anyway if you haven't booked a table. If you need to work, it will be necessary to upgrade to 1st class this costs £270 (€315). There is also a persistent fault with the toilets on this type of train that means sometimes there is a strong toilet smell.
Paris-Bordeaux takes 2h05m and is non-stop. If I go online now the next train is at 6:30pm and costs €60 2nd class. There is a non-stop train roughly every hour and there are also trains that stop 2-3 times that take about 3h but are a bit cheaper. The 2nd class seat is spacious your legs are about 5" from the seat in front and there is a table with enough space to comfortably use a laptop which has an individual socket and usb charging point per person. The ride quality is very smooth, you can easily use a laptop trackpad or mouse accurately enough to do CAD work, you wouldn't realise that you are travelling at 200mph. Edit: 1st class is available for €72 and did I mention that the train is double decker? it's just a lot cooler. Another edit: There are quite a few trains tomorrow with tickets for €29 and one train with a ticket for €12.50