London is exactly 1 hour behind Warsaw year-round. When it's 3:00 PM in Warsaw, it's 2:00 PM in London. Both cities observe DST on the same schedule.
Poland uses CET/CEST while the UK uses GMT/BST. The 1-hour difference remains constant throughout the year.
Any business hours work great! 9:00 AM - 5:00 PM London corresponds to 10:00 AM - 6:00 PM Warsaw. Full business day overlap.
Poland has one of the largest UK diaspora populations, with nearly 1 million Polish people living in Britain. Business ties in finance, manufacturing, and IT are significant.