A note on the LCY-TXL services, I went TXL-LCY this week and is was a remote stand with bus. The 16:50 departure went from an adjacent gate to Turkish Airlines, sharing security/passports, so the queue was a bit slow. I'd be cautious about using LCY B2B services, I imagine it would be even riskier if the inbound bus doesn't deposit you at the outbound gate.