I am currently looking for SIP trunks providers. I have one with our current PSTN provider 2circles.co.uk. They offer
£50 setup fee
10 DDI’s for £1.50 per month
1 SIP trunk £3.95 or 1 SIP trunk with 4000 minutes UK (mobile/landline) £11.95
That is pretty good for our rather low use with 12-13 extensions.
Any other suggestions? (My previous post was checking hosted BPX and port5060 was suggested, but they only offer SIP trunking when calling is more than £200).