You make it sound like open heart surgery eddie.Yup 2 x CR1220 batteries, gently prise open the radio key case, bearing in mind if he\she breaks it it will be expected that it is replaced with a new one, the batteries are slid out in the holding clip in a retaining ring, polarity checked, new ones replaced in the retaining ring, observing correct polarity. The new batteries in the retaining ring is slid back into the holding clip and the holding clip and then the circuit board is relocated into the case, including the fiddly key ring strap and the plastic case is carefully clipped back together, and knowing Timpsons, tested
A tenner!
As I say I don’t think that that is a ripp off