There is no requirement to deny a transit (at the moment) due to a lack of mode 'C'. If you're IFR you're at a known level anyway, so the only time you may cause a problem is during a long climb or descent (not likely in an airfields class 'D' - they're not that high
) when the Controller will use the mode 'C' to establish whether you have vacated a level without asking.
Sounds to me like you were unlucky at Teeside - possibly due to workload.