Hi,
That looks superb as a starting base,I would love to get some cab-end's to do a similar project, I do have an MTK 312 model which is nearly complete, I must admit that i never thought of an HST unit for power.I bought a black beetle when they were cheaper,which slotted into the Hornby bogies with no problems , evne although the bogies are not correct for the powered ones.Best of luck.