This is a good idea as long as you're sure you won't need these types of forces at short notice. If the coming war ends up being a "come as you are" affair where you don't have 6 months to bring the reservists up to speed before deploying, it's less satisfactory. Along the same lines it also presumes that the TA soldiers can be pulled out of their civilian employment more or less at will, and although that might be the case I'm not entirely sure it would be received in a supportive light if there wasn't a clear, obvious threat to the UK.
Would you accept a modification to the idea? Instead of having only cadre staff as Regulars, let's assume there is a small Regular force based around let's say an armoured division, itself composed of three brigades (each of one armoured battalion, two mechanised battalions, an artillery regiment, an engineer regiment, air defence and all the usual supporting arms). At any time one brigade will be acting as trainers for the TA units conducting their own training; another will be on "active" status as a rapid response force; and the third will be in the "quiet" phase of the cycle doing repairs and maintenance, integrating new recruits, and giving leave more liberally. After 6 months they rotate roles and start all over again.
This has the advantage that there is a rapid response force available at any time if needed, and it can be deployed without robbing the TA of cadre staff or requiring partly-trained forces to be committed. It also provides a structure for expansion of the Regulars if needed (each Regular brigade becomes the core of a new division, it's personnel spread out to provide cadre for the newly formed units).
There are other nations which have had to deal with reductions in defence spending, and they have generally come to the conclusion that while reserves are useful, they take too long to reach a deployable standard in time of crisis and that they are more useful as a supplement to the regulars rather than a replacement for them. I'm thinking particularly of the New Zealand experience post-2000, where the reserve formations provide round-out units in case of mobilisation but otherwise the emphasis is on having a full-strength and capable RRF (Ready Reaction Force). There's also been a move towards making it easier for TF personnel to take a turn in the regulars if they wish.
The same style of organisation might be possible for RAF units as well, although I'm less familiar with their roles and requirements.