The Kinetics 8-speed Brompton conversion uses a Sturmey Archer hub gear with a very wide range. No modification of the frame is needed. I can fit the 8-speed to a new bike for £200, or for your existing Brompton I can send you a kit for £300 (the new bike price is cheaper as I can reuse a lot of parts). The kit includes the complete back wheel, chain tensioner, gear shifter and cable, replacement chainset and bottom bracket. You’ll need a cartridge bottom bracket tool, a few spanners, and a few allen keys - fitting is not hard. Brompton 8-spd Kit - £300  - delivery takes 2 weeks | 
