... from accepting personal donations. That would cut out a lot of issues.
Donations should all go into a pot for the party to disburse them as it sees fit. MPs would need to apply for a share and make a case as to how they would be used.
Political parties partly rely on donations, no problem with that, but they should always be transparent - how much and who / where from and where spent. Cash only. No clothes, wallpaper, holidays, football or concert tickets.