Are you going to Lexus centre? or an Independent garage?
Where are you in Cambridgeshire? as i am close i could recomend my garage to you that i have had my last services done at.
Last MOT i had was £50 something...Battery im sure are about £90 from Halfords, a good charge may sort it before you go out and buy a new one.
rear pads, you could do yourself, there is a walkthough on here.