I am Sri Lankan, by the way in your case you cannot do anything unless you can find out the educational body for your diploma in india and contact them directly if they can help you on this,
these days many asians suffering here to attest their certificates, unlike earlier days the rules are very strict and hard , even for HND, BSc provided by private campus in srilanka under UK educational bodies nowadays not worth here and not possible to attest.. even in Common Wealth Organization in UK start to reject distance educations from them...