There's a benefit that can be claimed by all previous PMs (and it was extended to cover deputy PM Clegg), of up to £100K per year to cover any ongoing costs they may have that relate to having been in the job.
Someone put a freedom of information request in to see who'd claimed what. Rather unsurprisingly, just about all the surviving ex-PMs just claimed the entire £100K every year, including Blair and Clegg. Surprisingly, about the only one who didn't was Cameron. However, he did claim most of it, and he did stick his cock in a pig's mouth, so let's not give him too much credit for it.