Gents,
Perhaps I can help a little.
First, the question - yes, there certainly have been times when the RAF has been 'anti-cannon', as I'll confirm. Perhaps the bigger issues are the lack of understanding of what cannon can do, how they do it, and also what the required target set is.
The first two are basic - if the Air Staffs don't know how cannon work, or how to model their effects, they will usually reach the wrong answer. In my direct experience in the mid 90's there was an almost total lack of understanding in this area, across all staffs, including AWC. This was a long running issue.
This is why we had persisted with the Aden 30 for many years. This cannon (and its shell) was designed specifically (by the Germans in 1944) to knock down highly flammable bombers at close range. Thus a correct choice of a high rate of fire weapon plus a low velocity shell with a large charge to blow structure (and fuel systems) apart and start fires/explosions. However, the basic shell was almost ineffective against ground targets. Much better Aden 30 rounds using 'multipurpose' technology were offered for years by RO, with absolutely no interest shown by the RAF. However, they were successfully exported to many foreign users.
The Mauser 27 was a very good cannon with rounds designed for both air and ground use. The large shell gave good anti aircraft performance, the high velocity helped in ground use by extending range. However, it was eye wateringly expensive (around 15 times the cost of a 25mm round), as the calibre wasn't adopted more widely.
The modelling of gun system effectiveness at Farnborough in the 90s was limited and in some cases plain wrong. Some of the models used to assess the close in use of gun systems on the Typhoon were riddled with basic errors. There were no reliable models for assessing the effectiveness of various types of shells against jet aircraft structures. Most importantly, there was no appreciation of the huge impact that modern raiders and gunsights were having on the ability of gun systems to reliably hit a target. All these led to massively pessimistic estimates of air to air gun system effectiveness. (I'm talking 20, 50 or 100 times out here).
Things weren't helped when projects like the Aden 25mm cannon for the GR5 hit technical problems that were directly due to lack of investment in gun systems - our designers were not really up to scratch, and our biggest shortfalls were in gun/aircraft integration, especially in designing reliable ammunition feeds and link/cartridge disposal systems. And, to be honest, the Air Staff really weren't interested by that stage. The cancellation of the Aden 25 tossed away around £7m of spend when a targeted spend of £250K would have fixed the system. Fact was that the Air Staff were fixated on Brimstone, LGB and Storm Shadow by that stage.
The US have retained much better core knowledge and reliable effectiveness models. Plus, their Vietnam experience still impacts the USAF's approach. For the F-35, that is why the A model comes with an internal cannon, the B and C going for a pod. (Interestingly, the original choice for the cannon was the Mauser 27. This was overturned by very effective lobbying by the US gun firms, and a 25mm Gatling was adopted, which is heavier, bigger, and gets less bullets on target per firing pass - go figure). The external pod is a well designed and well engineered system, mainly due to the fact that GD have been doing it for years now.
The A-10's long cartridge 30mm gun system is simply huge and totally designed for air to ground use. To a large extent, the aircraft is designed around it. However, the Swedes and the French have shown what you can do to put a highly effective high rate of fire 30mm cannon into a strike aircraft.
Balancing all this for the RAF, however, was the basic (and correct) fact that for high end, hardened ground targets, guns don't deliver enough effect and present too much risk to the aircraft. In the end, scarce pounds (in my experience) tend to go to the highest end solutions that offer the most 'bang per buck' against the hardest target in the assessment models. (By the way, I never saw a model that used the cost balance between the missile and the target as a selecting parameter). That's why unguided rockets fell so far out of favour, although they offer very good 'bang per buck' in many situations. (Oh, and 'Their Generalities' did order TP variants for the CRV7 for the Apache - the RAF originally didn't).
My take on current issues is that the 'limited war' scenarios we now have are testing the 'high end' assumptions to their limits. A well designed high velocity cannon (or possibly a guided ticket solution like APKWS) could engage a wide variety of targets with very good effectiveness, at massively lower costs than we are now incurring. Plus we have increasingly effective DAS systems that can tackle the MANPAD threat (or at least greatly reduce the risk).
Hope this lot helps, sorry if I've gone on for too long
Best Regards
Engines