The Spanish family hatchback starts at £19,855 with the 108bhp 1.0-litre TSI unit. The eTSI mild-hybrid version, which uses the same base engine and is expected to appeal strongly with fleets, takes that price to £22,720 in entry SE trim.
Mated solely to an efficiency-boosting DSG gearbox, the eTSI uses a 48v starter-generator and small lithium-ion battery to allow engine-off coasting, enable energy recuperation under deceleration and provide torque assistance under acceleration.
Seat isn't yet quoting consumption figures for the eTSI, but in the related Volkswagen Golf the same unit is claimed to boost efficiency by around 10%. It's also RDE2 compliant, meaning nitrogen oxide (NOx) levels are below 60mg/km.
The Leon e-Hybrid plug-in sits at the other end of the range, with prices starting from £30,970. That mates a 1.4-litre TSI petrol engine with an electric motor and six-speed DSG gearbox, plus a 13kWh battery pack.
Resulting power is 201bhp, translating to a 0-62mph time of 7.5sec. More importantly, WLTP-standard CO2 emissions are down to just 27g/km, with economy quoted at between 217.3 and 235.4mpg.
The e-Hybrid can travel up to 36 miles on a single charge. However, it can only be topped-up via a 3.6kW AC inlet, with a full charge taking four hours. Likely to be a hit with business users, it attracts a Benefit-in-Kind rate of just 10%.
The Leon's sub £20k base price is for a 1.0 TSI model. Seat quotes a representative PCP lease price of £195 per month, based on a 4% APR rate and a £1000 deposit contribution. SE spec comes as standard with LED headlights, automatic high-beam, keyless start, a leather steering wheel and an 8.0in touchscreen infotainment system.