Joomla htaccess redirect to mobile site - .htaccess

Question

I am trying to get this joomla site to redirect to a subdomain called mobile.backuptoweb.co.uk when used on mobile devices. But I also want to keep the existing rewrite rules that ensure all users are redirected to the www. url and trailing / are removed.
Currently it just redirects into an infinate loop when view on a mobile device.
htaccess:
##
# #package Joomla
# #copyright Copyright (C) 2005 - 2012 Open Source Matters. All rights reserved.
# #license GNU General Public License version 2 or later; see LICENSE.txt
##
## Can be commented out if causes errors, see notes above.
Options +FollowSymLinks
## Mod_rewrite in use.
RewriteEngine On
## Begin - Rewrite rules to block out some common exploits.
# If you experience problems on your site block out the operations listed below
# This attempts to block the most common type of exploit `attempts` to Joomla!
#
# Block out any script trying to base64_encode data within the URL.
RewriteCond %{QUERY_STRING} base64_encode[^(]*\([^)]*\) [OR]
# Block out any script that includes a <script> tag in URL.
RewriteCond %{QUERY_STRING} (<|%3C)([^s]*s)+cript.*(>|%3E) [NC,OR]
# Block out any script trying to set a PHP GLOBALS variable via URL.
RewriteCond %{QUERY_STRING} GLOBALS(=|\[|\%[0-9A-Z]{0,2}) [OR]
# Block out any script trying to modify a _REQUEST variable via URL.
RewriteCond %{QUERY_STRING} _REQUEST(=|\[|\%[0-9A-Z]{0,2})
# Return 403 Forbidden header and show the content of the root homepage
RewriteRule .* index.php [F]
#
## End - Rewrite rules to block out some common exploits.
## Begin - Custom redirects
#
# If you need to redirect some pages, or set a canonical non-www to
# www redirect (or vice versa), place that code here. Ensure those
# redirects use the correct RewriteRule syntax and the [R=301,L] flags.
# mobile site redirection
RewriteCond %{HTTP_REFERER} !^http://(.*).backuptoweb.co.uk/.*$ [NC]
RewriteCond %{HTTP_USER_AGENT} "android|blackberry|iphone|ipod|iemobile|opera mobile|palmos|webos|googlebot-mobile" [NC]
RewriteRule ^(.*)$ http://mobile.backuptoweb.co.uk/$1 [L,R=302]
RewriteCond %{HTTP_HOST} ^backuptoweb.co.uk [NC]
RewriteRule ^(.*)$ http://www.backuptoweb.co.uk/$1 [L,R=301]
# index.php to /
RewriteCond %{THE_REQUEST} ^[A-Z]{3,9}\ /.*index\.php\ HTTP/
RewriteRule ^(.*)index\.php$ /$1 [R=301,L]
#
## End - Custom redirects
##
# Uncomment following line if your webserver's URL
# is not directly related to physical file paths.
# Update Your Joomla! Directory (just / for root).
##
RewriteBase /
## Begin - Joomla! core SEF Section.
#
RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]
#
## End - Joomla! core SEF Section.

Answer 1

Would it be feasible to redirect all mobile traffic to your mobile subdomain and have a second .htaccess file there where you do the mobile tests and rewrites?
To check if I understand your comments correctly,
For non-mobile visitor
http://backuptoweb.co.uk/something redirects to http://www.backuptoweb.co.uk/something
For mobile visitor
http://backuptoweb.co.uk/something redirects to http://www.mobile.backuptoweb.co.uk/something
except if they are coming from your mobile site. If this is the case you want
http://backuptoweb.co.uk/something redirecting to http://www.backuptoweb.co.uk/something
What do you think of this for the logic and order?
Rewrite index.php to / (definitely don't use [L] flag)
Check if mobile visitor and coming from mobile site. If yes use Rewrite with [L] and send to http://www.backuptoweb.co.uk/something
Check if mobile visitor (and not coming from mobile site. If yes use Rewrite with [L] and send to http://www.backuptoweb.co.uk/something
Rewrite no-www to www.backuptoweb.co.uk/something with [R=301,L]
Some of the flags probably need work.
See how this works for you. Be sure to clear you browser cache as well when testing.
If there are any mod_rewrite gurus out there, I'd also welcome suggestions for improvement
Options +FollowSymLinks
RewriteEngine On
# Jooomla stuff here
# rewrite index.php to /
RewriteCond %{THE_REQUEST} ^[A-Z]{3,9}\ /([^/]+/)*index\.php\ HTTP/
# RewriteRule ^(([^/]+/)*)index\.php$ http://www.backuptoweb.co.uk$1 [R=301] *** updated
RewriteRule ^(([^/]+/)*)index\.php$ http://www.backuptoweb.co.uk/$1 [R=301]
# check if coming from mobile site
# if yes continue to main site
# RewriteCond %{HTTP_REFERER} ^http://www\.mobile\.backuptoweb\.co\.uk/ [NC] *** updated
RewriteCond %{HTTP_REFERER} ^http://mobile\.backuptoweb\.co\.uk/ [NC]
RewriteRule (.*) http://www.backuptoweb.co.uk$1 [R=301,L]
# send any remaining mobile visitors to mobile site
RewriteCond %{HTTP_USER_AGENT} "android|blackberry|ipad|iphone|ipod|iemobile|opera mobile|palmos|webos|googlebot-mobile" [NC]
RewriteCond %{http_host} !^$
# RewriteRule (.*) http://www.mobile.backuptoweb.co.uk/$1 [R=301,L] *** updated
RewriteRule (.*) http://mobile.backuptoweb.co.uk/$1 [R=301,L]
# rewrite non-www to www
RewriteCond %{http_host} ^backuptoweb\.co\.uk$
RewriteCond %{http_host} !^$
RewriteRule (.*) http://www.backuptoweb.co.cuk/$1 [R=301,L]