You need an embassy visa for United Kingdom if you have a Ukrainian passport
Visa options for United Kingdom
Visitor visa
Travellers need a visa to visit United Kingdom for Business or Tourism. A paper or embassy visa is the only visa available for travellers visiting United Kingdom. The visa is typically a stamp or sticker added to the passport. Travellers must obtain this visa from a local embassy, consulate or visa center before travelling. Beginning 0001 GMT 13 February 2025, nationals of Ukraine will no longer be able to use permission to travel letters (issued under the Ukraine visa schemes) to travel to the UK when no entry clearance or digital status is held. Check the source for more details.
This is not offered by sherpa°.
Apply on the government site.