I can think of several areas where savings can be made.
1. Cancel the £22bn carbon capture project - it is untested and will not make any major contribution to reducing global CO2 emissions.
Trend to agree, it's of limited value, when you could probably get a larger reduction from other investments (for example public transport and walking/cycling infrastructure/support or creating wetlands - which are larger carbon sinks than forests when addresses by area).
Although, even then it's a resurrection of spending rather than cutting.
2. Cancel foreign investment in 'green schemes' and audit foreign aid for Value for Money. There are a number of schemes Britain has invested in which seem to be pointless - e.g. Ethiopian 'Spice Girls', and why are we giving money to India when they can afford to invest in a space programme?
A lot of this is actually useful in projecting the soft power of the UK and therefore creating people who think positively about the UK. That may not sound like a good thing, other than it limits the risk of people having negative reactions to the UK (i.e. it becomes harder to radicalise someone to cause us harm if they've received food and/or education from us).
The other thing it does it boosts the education of girls, which means they are less likely to end up getting married off at a young age. Whilst someone in Ethiopia doing something space related may appear odd, by engaging then in STEM they are more likely to have aspirations to have a good job.
Those aspirations could then result in them going to university, which could mean doing so in the UK. Whilst that's not always going to be the case, if they do, that than results in them spending money in the UK and paying overseas student fees (which is a significant income for UK universities and means UK fees can be frozen), in fact part of the issue in the university sector is the cuts to the number of overseas students which are allowed (even though over the long term they tend to have limited impact on the net migration figures and they tend to leave within 5 years of arriving).
3. The number of people qualifying for Motability cars seems unduly high - there are about 800,000 cars according to motability.co.uk, and they are replaced every three years which seems unduly frequent.
Given that there's 16.1 million people with some form of disability for only 5% of them to qualify for a Mobility car doesn't sound like the numbers are overly high.
Yes there could be some who shouldn't have one, but that's not going to have a significant impact on the overall numbers.
Likewise, the three year period is so there's not the hassle of having to deal with getting the vehicle through an MOT.
4. The number of Civil Servants in the MOD increased whilst the number of armed services personnel fell. There are now approximately 120,000 armed services personnel in the three services, and around 64,000 Civil Servants in the MOD; there must be some scope to reduce the number of Civil Servants.
Given the push towards cyber security defense (and they are likely to be counted as Civil Servants rather than armed service personal) that could at least explain some of that increase.