Cleaning velour can be tricky.
My old V40 had velour seats and I cleaned them every year by spraying Autoglym Upholstery Cleaner straight on to the fabric. I then used a Vax machine with warm clean water in to wash the fabric and suck the detergent and muck out of the fabric. Always done in the summer on a warm day so the seats dried quickly. The car covered 370,000mls and the seats were like new when scrapped. In fact the scrappie I sold it to listed the seats on ebay as rare immaculate seats from a low mileage car.
By contrast, 'er indoors Mk 4 Fiesta had velour seats, but the Vax would not work on them at all. The upholstery head would not slide across the fabric and even when held stationary there was no suction to get the water flowing. I ended up just wiping them over with a damp cloth and Autoglym. The seats never looked truly clean.