The basic plan would be to meet at Hitchin Station and catch the 18:02 into King’s Cross. From there your train ticket, which covers the underground too, would allow you free reign around the sites of London with a suggestion that the Thames would offer something for everyone.
After a couple of hours photography, the plan would be stop for a quick drink before returning around 10:00/10:30.
Rob suggests that the train tickets could be brought as a group and would be around £12.50 each. Having done a couple of these evenings before Rob the light evenings may even let you get away without taking a tripod.
If you’d like to learn more, or would like to reserve yourself a place for the 20th, just contact Rob at www.lamaisonblanc.co.uk