Just caught up with an article in the previous Sunday Times forecasting some dramatic changes to the UK military, on the back of a substantial increasing in spending.

Upgrading the Challenger tanks I mentioned separately today, but in other respects the traditional hardware is in for a hard time, with the focus being on high-tech R&D, AI, cyberwarfare, drones, etc. The army is taking the biggest hit, with the aim being to turn it into a sort of USMC outfit, involving a further cut to troop numbers (down to c.70,000) but giving them the latest kit. The long-planned upgrade to 600 Warrior MICVs is likely to be cancelled, and presumably the vehicles disposed of, while the AS90 155mm SPG and MLRS, plus towed howitzers, are all to be replaced by "attack drones" and PG rockets.. This will leave the new Ajax family as the only tracked AFVs apart from Challenger. 

One major cut affecting the RAF is that of 90 of the planned 138 F-35B, which means there will probably be only enough bought to put on the two new carriers (24 each, not allowing for some based ashore for training etc). The UK is focusing on the new Tempest fighter planned for service entry in 2035 - that will replace the Typhoon. Over 40% of the helicopter fleet will be scrapped plus the SAS Hercules fleet and various electronic warfare planes. For the RN, new frigates will be bought but some frigates and subs will be retired as past their sell-by dates.

Whether all of this is agreed will be known later, and then whether it will be implemented is another matter. Like most other militaries acquiring hi-tech stuff,  the UK MoD has a poor track record in delivering such projects on time and within budget - or even at all.

Does total budget remain the same, with the differences just being the priorities?

No, there's supposed to be an extra £16 billion over four years to pay for new equipment.

The Army can see it's in the firing line, so is getting its retaliation in first: https://www.bbc.co.uk/news/uk-56386446

The BBC News website is giving the defence review top billing - now that is unusual... https://www.bbc.co.uk/news/uk-56410532

More details re AFVs:

After £430 million, ten years and the recent completion of over 80 percent of its long-delayed trials, the UK’s Warrior Capability Sustainment Program is no more. The axing of the much-maligned program was announced in the Defence Command Paper released yesterday by the Ministry of Defence.

The Command Paper states that “legacy platforms that have already been extended beyond their planned life” will need to be retired, in order to free up funding for the accelerated procurement of the Boxer Mechanised Infantry Vehicle. As a result, the Warrior Capability Sustainment Program being undertaken by Lockheed-Martin UK has been cancelled, with no operational Warriors to receive any of the upgrades of the program. Warrior, initially known as MCV-80, initially entered service in 1984. The unupgraded Warriors will continue to serve until their expected out of service date “by the middle of this decade”, after which they will be replaced by Boxers.

I rather suspect that the Warrior upgrade was cancelled because it could be, rather than any technical reason.

The Warrior upgrade has struggled on for so long (and with the cost estimate steadily increasing, of course) that there has been a lot of criticism of spending so much money on upgrading an old and unsatisfactory vehicle. There has long been an argument that it would be far better, and cost not that much more, to buy more examples of the Ajax MICV family instead, so it is interesting that the proposed alternative now is to buy more Boxers.

I suppose the argument might have gone something like this: the main reason for having a tracked MICV is to keep up with the tanks off-road. But the number of tanks is dropping so low (c. 150) that we've probably ordered enough of the Ajax already to cover that requirement. So boosting the 8x8 family might make more sense.

Except that no IFV have been ordered in the Ajax family of vehicles.

Given the UK has left the EU, it seems like it would make sense to reduce their 'land' based assets vs naval and air forces. 

For NATO, really the continent of Europe should be providing the land based weapons, not an island the furthest distance from Russia. Whereas NATO is not very heavy on Naval power and so-so in the air. 

And for partnering with the US, really Naval power, or the deployment of SF / Marines, is what would be complimentary. 

And of course for defending the UK or securing its interests abroad independently (Falklands 2.0?) that also speaks to a Naval and Air force with SF + Marines. 

So I think its pragmatic to be shifting focus from tanks and AFV's given budget constraints.