A dielectric-lined waveguide has been designed for use as an accelerating structure in terahertz-driven electron acceleration experiments at Daresbury. Experimental verification of acceleration will take place on Versatile Electron Linear Accelerator (VELA). The choice of a rectangular waveguide structure with sidewall dielectric layers enables tuning by varying the spacing between dielectric slabs to account for potential manufacturing errors. Schemes for coupling free-space single cycle THz pulses into the waveguide have been evaluated and optimised through CST simulation. Comparison of simulation with experimental measurements will also be presented.