Hi Richie L.
There is normally no cut in your benefit during the first 28 days in hospital, unless you had been in hospital or a care home in the 28 days before your current hospital stay. If you have a partner and both of you had been getting a qualifying benefit, you keep the premium (SDP) even after your qualifying benefit stops, but at the single rate.
ESA: You can continue to receive 'new style' or contributory ESA while in hospital or a care home.
IR ESA: As above, there is normally no cut in your benefit during your first 28 days in hospital, if you are entitled to IR ESA because a severe disability premium is included in the award, when the premium stops at the 28 day stage you will loose the IR ESA.
You can continue to receive IR ESA for the duration of your stay in hospital, any premiums and the work related activity or support components in IR ESA will stop after you have been in hospital for 52 weeks. ESA Regs, Sch 5, para 13
www.gov.uk/going-to-hospital-benefits Gary