The calculated distance (air line) between Swadlincote and Southend-on-Sea is approximately 129 miles respectively 207 kilometers.
By car or train, the actual journey to Southend-on-Sea is certainly longer, as only the direct route (as the crow flies) between Swadlincote and Southend-on-Sea has been calculated here.
Air line (approximately)
207 kilometers
112 nautical miles