For best budget you would go from London Luton to Vilnius Lithuania 🇱🇹 for about £35 return on Ryanair or from north of England in Wizzair for maybe even less.... you would then have to get the Belavia (£95) return (your national airline) from Vilnius if you choose dates good your probably looking at a total of £130 a person for this journey... unlikely to get it much less!!!! And not direct!! When I went to Minsk I went via Kiev!! I also met a girl from Minsk and flights cost me £130 to get her from Minsk to Kiev... problem with Belarus is for visa free you have to go via Minsk airport with is mainly Ukrainian and Belavia flights....