t80si and rebranded models of the same sold at Homebase,Argos etc I seem to remember are very simlar layout inside. The electrical terminal block may be a couple of inches different but the water connection is the same. The later T80xr models I think have the terminal block further away still. You can probably still get the T80si itself but it's usually a lot dearer than these superstore offerings,and it is effectively the same shower.
Would say almost definitely the following will be same internals to the T80si:
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