RM 2nd Class - 0.038 BTC (£2.60)
RM 1st Class - 0.045 BTC (£3.00)

If you want to use escrow then:
RM Signed For 2nd Class - 0.055 BTC (£3.70)
RM Signed For 1st Class - 0.06 BTC (£4.10)