Right, I'm home.
If I understand you correctly (which I probably haven't - see below), the web server, www.specialservice.org.uk,
uses a private IP address on the LAN side of Router 1 and this LAN is part of the same subnet as the LAN side of Router 2. The webserver has a DNS entry in the real world that is an IP address on the WAN side of Router 1 and internet requests for www.specialservice.org.uk
are port forwarded to it.
You want LAN side clients to access the webserver by its LAN address and not go all the way out to t'internet and back in again.
A cheap but proper fix would be to set up a DNS server on your LAN to answer all DNS queries for LAN clients.
For this I would use a Raspberry Pi set up as a recursive DNS server for LAN clients with it authoritative for the specialservice.org.uk zone.
Set your DHCP server to give out the IP address of this as your only DNS server and set all static IP clients to use this server.
The whole setup can be done very easily with the Raspbian Jessie Lite or Arch Linux distributions (I use both).
You could used Webmin if you wanted a GUI to administer the DNS server.
Total cost of hardware is about £52 from Amazon for a Raspberry Pi 3, official Pi 3 power supply, case and 32GB class 10 micro SDHC memory card. The software to do this all is free. It just takes a little bit of setting up. If you have an experienced Raspberry Geek this would take about 40 minutes from scratch including installing the operating system, software, applying updates and configuring the DNS zone for specialservice.org.uk.
I run a number of Raspberry Pis as internet and LAN facing nameservers and they're rock steady and use very little electricity. Clone the SD card of a working setup and you have instant disaster recovery for about £7.
What's not to like?
Edited by caffn8me (Sat 09-Jul-16 01:44:27)