As the DPE is limited to two licensing events per day and signing your paperwork counts as one event, you can expect to pay for the privilege as reported by matthew.
This was changed in 2018 to three per day.
And in order to exercise IR privileges, do I need IFP or IPC or both?
Just the IFP exam is required. No endorsement needed but make sure you create your FTN on IACRA first.
once issued, you need to complete ... an IPC before exercising your IFR privileges
I don't think this is the case. An IPC is only required to regain instrument currency, so if you are already instrument current, there is no need to do an IPC.
There are at least two DPEs in the UK.
Interesting.... I wonder which FSDO they report to.