If you place the spring JAR file(s) somewhere other than within your WAR file, it should work. You could, for example, create an EAR, place the common JARs in the EAR's lib directory, and place your two WARs within the EAR. The whole thing could be set up using exploded deployment.
That sounds interesting, I shall have a think as I also have another potential solution (that I don't like much) and then look into the exploded deployment. Thanks for the reply.