Yes, you can buy car insurance for one day. Short term insurance like this is a tried and tested product with hundreds of thousands of regular users. Prices are very reasonable, buying a policy is extremely quick and easy, and since it is done online you can get a policy at any time of day or night you wish, from the comfort of your own home. Policies can be bought for between a single day and a maximum of 28; and although there are certain conditions (for instance you must be over 19, with a reasonable car to insure and a fairly decent driving record) the vast majority of motorists, whether British born, temporary residents or visitors, will have no problems with the short proposal form.
You can insure a car which belongs to you, but which you have perhaps kept off the road for a while; or you can cover a vehicle that you have borrowed from a friend, neighbour, relative etc. Alternatively you can lend your own car to someone else who can insure it in a similar way. Provided that the car you wish to cover is registered in the UK, is unmodified and is not a personal import it is likely to be on the insurers' database, which means that it can probably be covered.
You can apply if you have a full driving licence from any of these countries which you have held for at least a year. UK learner drivers may also be accepted. Non-UK residents should provide their temporary UK addresses on the application form, not their home addresses.
The simple proposal form only takes a matter of a minute or so for getting a quotation; and then provided that you have the registration details of the car you want to cover it is only another couple of minutes before you can pay for the policy online and download your documents.
You have the choice of either arranging cover to start at some time in the near future, or immediately. This means that you can have your insurance arranged in good time if you are going to need it soon, but in an emergency it can be arranged extremely quickly.
Obviously on a cost-per-day basis a full year's policy usually works out cheaper but short term cover can still be surprisingly economical and premiums are generally far lower than they were before specialised companies came into the market. Plus: some insurers give a lowest price guarantee! it only takes a very short time to get a quote so why not see for yourself.
All insurance companies operating in the UK have to be authorised and regulated by the Financial Conduct Authority which of course gives access to the Financial Services Compensation Scheme in the unlikely case of an insurer becoming insolvent.
You are sent a link to your documents a moment or two after you have bought your policy. You can download these and print them on your home printer if you wish, but this is not a legal requirement. However, bearing in mind that the details of the insurance cover will probably not be on the Motor Insurance Database (which police forces check up on from time to time) for several days it is very advisable that when you are buying any insurance, including short-term insurance, you carry the cover note with you for the first few days just in case you need to present it.
Car insurance for one day can be a very useful product indeed, so you may wish to bookmark this site - you never know when you may need it in the future!