Any decent tyre fitting bay will thoroughly clean the rim bead and brush paint on a rubber sealing compound. Tyre fitting then proceeds and the sealer is forced into any gaps between the rim and the tyre. I had four new tyres fitted over a year ago and the fitters used this methodology. A year after fitting, I`ve not had to adjust tyre pressures once. Those guys did a great job.
£20 per tyre seems excessive to me. At least Dick Turpin wore a mask..... I`d change tyre fitters and find another hopefully with a more helpful attitude.
Mobile tyre fitters will charge more than Syd Snott & Son (on the corner of Peckham Broadway and Gas Works Alley)
My lot down in Crayford charge £12.50 per wheel and that includes balance and new valve.
They're good boys. They take cash
Gone: '59 Mark I, '56 Mark VIIM, '59 Mark IX, '01 XJ8 Sovereign 4L LWB, '01 XJ8 Sport 3.2L, '01 XJ8 Exec 3.2L
Current: '03 Strange Rover L322
In trim shop for total refurb: '73 Owen Sedanca 4.2L
Stalled in storage '61 Mark IX with 4.2L