The calculated distance (air line) between Stansted Mountfitchet and Birkenhead is approximately 170 miles respectively 273 kilometers.
By car or train, the actual journey to Birkenhead is certainly longer, as only the direct route (as the crow flies) between Stansted Mountfitchet and Birkenhead has been calculated here.
Air line (approximately)
273 kilometers
147 nautical miles