Cisco WAN :: 1941 / K9 / How To Route Internet Traffic Through MPLS

I am working for a company based in Sydney Australia, the company recently open an office in London UK, therefore we are going to get leased lined based on MPLS.We were advised that Customer Edge router will be CISCO1941/K9. We want to our UK client to access our web-based applications via MPLS network instead of internet. The UK office is using BT Business ADSL with 5 Static IP address (please note the modem IP address is actually dynamic), we are going to get a Cisco 857/K9 router which will be used for the entry for the UK client to access the MPLS network. My question will be how do I configure the Cisco 857 router to allow one of the public ip to access the MPLS network. It appears that there are two options, and I am not sure if this is going to work or which one is working better. I have attached two diagrams for clarification of my case.
 
Option 1 Cisco WAN interface get Dynamic IP (PPPoA) from BT LAN Interface (4 Port) get the assigned 5 Static IP addresses One of the five IPs (217.xx.xx.169) will be assigned to the FE1 (Cisco 1941), any traffic to 217.xx.xx.169 will be routed to the WAN interface of Cisco 1941 to access Sydney service (located in Sydney LAN, mostly http and https traffic) One of the five IPs to 217.xx.xx.170 will be assigned to the WAN interface of Sonicwall Firewall Router which also serve as Internet Access Gateway for LAN users, All trafiic destined for Sydney LAN will be using FE0 (Cisco 1941) as gateway
 
Option 2Cisco WAN interface get Dynamic IP (PPPoA) from BT LAN Interface (4 Port) will get 192.168.0.1, Cisco 857 router will be the default gateway for LAN users, using one to many NAT, also one to one NAT, One of the five IPs (217.xx.xx.169) will be forwarded to the FE0 (Cisco 1941), any traffic to 217.xx.xx.169 will be routed to the WAN interface of Cisco 1941 to access Sydney service (located in Sydney LAN, mostly http and https traffic)