Tarnish,
Best I can find:
<a href="http://www.ukembassy.gov.bh/consular/bahvisa.htm#visarules" target="_blank">http://www.ukembassy.gov.bh/consular/bahvisa.htm#visarules</A>
Seems that 4 weeks(2+2) is maximum stay for "temporary" visa.
I believe that you can also drive a car on a full UK licence for a month, but with an international licence for longer than this.