Right try this out,
GeoIPEnable On
GeoIPDBFile /var/www/GeoIP.dat
RewriteEngine on
RewriteCond %{QUERY_STRING} action=register
RewriteCond %{ENV:GEOIP_COUNTRY_CODE} !^GB$
RewriteRule ^index.php$ blocked.php [L]
*/*/*/GeoIP.dat may have been confusing it, stick so the full address or maybe you meant ./././
I hate RewriteCond confusing I had to use action=register otherwise you could change the url to ?blah=foo&action=register or ?action=register&anything to get around it.
I'm going to try and figure out how to have the RewriteCond only allow UK, without having to block every other country code.Figured that out just have to use !
