I do business in two other EU countries as well as in (still in EU 
) UK.
I’m unsure what business expenses in these other EU countries, if any, can be reclaimed, since my company is VAT registered in the UK.
With this in mind, when logging my expenses in these countries onto Quick file do I manually add the VAT (eg 25% for purchases in Denmark) even though it’s not certain I’m eligible to reclaim it?
You can’t reclaim non-UK VAT on a UK VAT return, so you shouldn’t record VAT on these purchases in the normal way. There is a scheme you can use to reclaim each country’s VAT from that country’s authorities as long as you don’t make any VATable sales in that country (dispatches of goods and “reverse charge” B2B services, where the buyer accounts for their own VAT, are ok). If you qualify for that then you may wish to track the VAT you intend to reclaim via its own nominals or foreign currency bank accounts but you can’t track it via the normal control accounts as they’re only for UK VAT.