2m coverage

Currently im using a Kenwood TM 251e 2m mobile rig (10W) with a 'Knocked up' J-pole... My local repeater is GB3SC and as you can see from the map im roughly in the center of the coverage (red star icon).

Now, the repeater is only about 9 miles away (Bournemouth GB3SC) and im told i can get into the repeater ok but i only ever manage to contact someone either between me and the repeater or the other side of me towards the Southampton repeater (GB3SH) but never manage to hear anyone the other side of either repeater.. I was told by someone that lives between the Bournemouth repeater and the Weymouth repeater (GB3DR) that he always hear's alot his side so what am i doing wrong? Any ideas as all i can usually hear is the local Echolink repeater which is very close to me (MB7IBH)...