The Phone System Checklist for UK Businesses Opening a Second Office

You are opening a second office. Your to-do list has 200 items. The phone system is item 187. It should be item 5.

I have helped 60 UK businesses expand from one office to two. The phone system decision made in week 1 either saves months of hassle or creates years of problems. Here is the checklist.

The Decision: Extend or Replace?

Your Current System	Recommendation	Why
Cloud VoIP	Extend	Add users in admin portal, ship phones, done
On-premise PBX (< 3 years old)	Replace now	Cheaper than buying second PBX + connecting them
On-premise PBX (> 3 years old)	Replace now	Maintenance costs + second PBX = 3x cloud cost
BT landlines	Replace now	Cannot extend landlines to new site

If you are on cloud VoIP already, adding a second office takes 30 minutes of admin portal configuration. If you are on anything else, now is the time to switch — before you are managing two legacy systems instead of one.

The Second Office Phone Checklist

Week 1: Numbers and Routing

• [ ] Get a local number for the new office (different area code = local presence)
• [ ] Decide: does the new office share the main number or have its own?
• [ ] Configure ring groups for the new office team
• [ ] Set up overflow: if new office is busy, overflow to main office
• [ ] Configure internal extension range (e.g., 2000-2099 for office 2)

Week 2: Network

• [ ] Verify broadband at new office: minimum 10 Mbps upload for 10 users
• [ ] Configure QoS on new office router (DSCP EF for voice)
• [ ] Disable SIP ALG on new office router
• [ ] Test jitter and packet loss during peak hours
• [ ] Set up voice VLAN if switch supports it

Week 3: Equipment

• [ ] Order desk phones for reception and shared spaces
• [ ] Deploy softphone apps on all laptops
• [ ] Deploy mobile apps for mobile workers
• [ ] Test every phone: inbound, outbound, transfer between offices

Week 4: Go Live

• [ ] Port local number to new office (if keeping existing number)
• [ ] Update auto-attendant: add new office as menu option
• [ ] Test inter-office transfers (office 1 → office 2)
• [ ] Verify caller ID shows correct office on outbound
• [ ] Quick reference cards at every desk

The Costs

Approach	Setup Cost	Monthly (10 users)
Second PBX + PRI circuit	£15,000-25,000	£1,200-2,000
Extend cloud VoIP	£0-1,500 (phones only)	£240

Cloud VoIP second office: £240/month. Legacy second office: £1,200-2,000/month + £15,000 upfront. The decision is not close.

DialPhone makes multi-site expansion trivial. Add the new office in the admin portal, ship pre-configured phones, connect the same CRM integration. One system, one bill, one support team across all locations.