I have a copy of RV Jones' book "Most Secret War", I read all the references to IR research and development, and if the contents of Jones' book are to be believed, they were ay least equal to the germans in IR Research. Certainly in airborne research the british possessed a technological lead, however they abandoned this in favour of Radar R&D. The research that had been done, appears to have been passed onto the Army, the Navy, and the Americans, who did develop IR technology very successfully, and utlized it extensively on Okinawa, where approximately 30% of the casualties inflicted on the japanese by small arms were attributed to these specialised pieces of equipment.
In England, the idea of using IR radiation to undertake attacks at night was first mooted in 1916. AB Wood undertook experiments in 1927, on airborne detection, with unpromising results. Official government sponsored research began at the end of 1934. By October 1935, an experimental IR aircraft detection system had been developed to a functional, but experimental state, by Jones and Anderson. A report to the air ministry at the end of 1935 was that the apparatus was functional, but had disappointing performance.
The main problem at the time was that the IR emissions from the engine were rapidly absorbed by the CO2 in the atmosphere, as well as airborne water vapours. The detection devices available at that time (1935) did not have the power to detect IR signatures at more than very short ranges. Despite the problems reported by Jones, he was directed to continue research by the air ministry,
Work on the IR detectors continued into 1936, under the overall direction of Tizard. This R&D effort led to the development of a workable electronic amplifier. By June 1936, the equipment was able to detect the aircraft in flight, but the big drawback as noted by Jones, in all IR systems (Allied or Axis) was its inability to determine ranges accurately.
April 1937 an airborne IR detection device was successfully tested. The equipment had been tested and developed to the point that even damped and screened engines could be detected...suggesting a considerable development of the technology. The sensitivity of the equipment was such that it could even detect the heat being emitted from the wing fuselage leading edges of the test aircraft...
In December 1937, a partial breakthrough occurred with the ability to determine ranges, using optical pulses. Methods were also found at about this time to reduce scatter in the lower atmosphere and in humid or damp conditions.
July 1937, the air defence subcommittee recorded in a report to the MOD "considerable progress has been made in the IR development work.....(and) should continue in view of the possibleapplication to other problems". Given subsequent diversification to a joint services research committee, it seems that the british even at this early stage were considereing parallel uses at sea and on land for the technology
In March 1939, the air ministry work was halted, temporarily, as a result of pressure from Watt (who wanted AI radar to be concentrated on). However, after the promotion of Watt, this decision was reversed, and the research taken up by an Interservice group, with the work to be undertaken at the Admiralty Research Labratory at Teddington
After this Jones account is silent, because he was transferred out of the project.
He later served on a special Intelligence gathering group, dedicated to analysing German progress on various filds of research. The only other reference to IR I could find in the book was that in 1942, a breakthrough on german research into IR revealed that they were at about the same level of devbelopment in 1942, as the British had reach at the end of 1938
I believe that the germans were the world leaders in tank design, but the claim that they led in all manner of electromagnetic radaition research is just not supported, at least in the area of IR research.