18/20mm lens up to 100mm

[Beav]

Hello! Im currently using a 10-20mm sigma, 18-55mm kit lens and a 55-250mm zoom lens. Eventually ide like to buy a 100-400mm L lens for motorsports but that won't happening yet. For the time being ide like to get a lens to carry me from 20mm (or even 17/18mm) up to 100mm or around that. Ive seen a 18-135mm canon lens for around £200 but im thinking at full zoom it won't be so good? Any recomendations for a lens to carry me from 17/20mm up to 100mm?

Thanks