When you look at BE's route network, outside of the business routes it's a bit random.
French routes are mainly served by MAN, BHX and SOU.
Italy is a mixture;
FCO - CWL only
MXP - MAN, BHX, CWL, SEN
VRN - CWL, SOU
VCE - CWL only
Germany;
HAM - BHX only
TXL - DSA, BHX, CWL
DUS - LBA, MAN, BHX, LCY, CWL, SOU
CGN - SEN only
HAJ - MAN, BHX
STR - BHX only
MUC - CWL only
SEN has a good mixture of longer routes, granted these are Stobart routes.
Aside from SEN, CWL stands out as having the most routes operated from there but not from the other bases. BE surely have the right sized aircraft for regional flying to some of these other destinations.
When you look at the SEN routes operating to further away - Croatia, PRG, BUD, VIE, these could be further routes and markets to expand in.