If price does not state plus VAT is it deemed VAT inclusive?

Yes, please see below Value-Added Tax Act, 1991 (Act 89 of 1991)

Part X - Miscellaneous

64. Prices deemed to include tax

1) Any price charged by any vendor in respect of any taxable supply of goods or services shall for the purposes of this Act be deemed to include any tax payable in terms of section 7(1)(a) in respect of such supply; whether or not the vendor has included tax in such price.