1. Yes. A standard US instrument rating may be included in your US private pilot certificate that was issued in accordance with 14 CFR 61.75. However, unless you have received the appropriate solo endorsement, you cannot operate as pilot-in-command of a US-registered civil aircraft at night regardless of whether an instrument rating is held.
2. Yes. The Airmen Certification Branch certainly needs another form AC 8060-71. I expect UK CAA will need a new form SRG 1160 also.