@Xenia
"Lots of them are not under the law asylum seekers but instead economic migrants,"
Actually, that's a complete lack of understanding of the law. Anyone who applies for asylum is, by definition, an asylum-seeker until their status is determined. Anyone is entitled to undergo a refugee status determination procedure. You don't get to say whether someone from Iran or Pakistan is or is not a bona fide refugee - that's what the refugee status determination procedure is for. It is entirely feasible that a national of Pakistan or Iran could have reason to flee their home due to human rights abuses e.g Christian in Pakistan or dissidents in iran.
If an asylum seekers claim is successful, that person has been determined to be a refugee and entitled to international protection. Conversely, if a claim is unsuccessful, then that person is, legally, not a refugee nor an asylum seeker and can legitimately be deported
Furthermore, the legal status of a refugee, as per the 1951 convention of whcih the UK is a signatory, is entirely linked to the reasons that they had to flee their homes and not whether they sought protection in a neighbouring country or decided to seek protection further afield. Refugees do not have to stay in the first country they arrive in in order to be considered a refugee.
Additionally, since you are concerned about the economic burden, why don't you lobby the home office to allow asylum seekers to work? The vast majority want to work to support themselves and their families but are forced to live off benefits.