I've fed in various cafes in Leeds too. Mainly in North Leeds:-
Chapel Allerton
LS7 cafe- very baby friendly and helpful staff. Quite open plan though.
Cafe Nero
Alwoodley/Moortown
Sainsbury's cafe at Moor Allerton Centre is ideal for practising as is like a creche during the day. It is very spacious and also has sofas.
There is also a breastfeeding cafe at the red brick church near here on Thurs pm.
Lord Darcey pub!- huge and lots of quiet corners
Roundhay
Lakeside cafe- seats not v comfortable and a bit close together but full of Mums.
Napa-Very helpful staff
The Roundhay Fox- lots of quiet areas, lots of Mums and by the park.
Lawnswood
Lawnswood Arms pub- is a Wacky warehouse so very child/baby friendly. Very spacious so can find a quiet corner. Food cheap and near Golden Acre park so could go for a walk.
Headingley
Costa
Starbucks
Citrus cafe- have fed in all Citrus was dead, so could be a quiet place to practise.
Salvo's restaurant- staff friendly- baby fell asleep being BF and stayed put for duration of meal.
Otley
Buon Apps restaurant
Hyde Park
LS6 cafe. Used to be post natal pilates upstairs so obviously baby friendly.
City Centre
Nandos!- has good booths too and they sat us in a nice quiet corner.
Also Fodder in Harrogate and Fennel In Wetherby tend to have plenty of Mums in the day.
Out of all of the above I would find Sainsbury's cafe, The Lord Dracey Pub, The Lawnswood Arms and The Roundhay Fox best to begin with....3/4 pubs! Really just because they don't have big windows, are spacious and have sofas/booths.
After all this you're probably in South Leeds!