The present invention relates to novel compounds of formula (I) or a salt thereof: wherein: G is a 5- or 6-membered heteroaromatic group, or is a 9- or 10-membered bicyclic heteroaromatic group containing one or two heteroatoms independently selected from nitrogen and oxygen, wherein G is not pyridyl, indazolyl or benzothiazolyl; p is an integer ranging from 0 to 4; R1 is independently selected from a group consisting of: halogen, hydroxy, cyano, C1-4alkyl, haloC1-4alkyl, C1-4alkoxy, haloC1-4alkoxy, C1-4alkanoyl or SF5; or corresponds to a group R5; R2 is hydrogen or C1-4alkyl; n is 2 or 3; X is S or —CH2—; R3 is C1-4alkyl; R4 is hydrogen, or a phenyl group, a heterocyclyl group, a 5- or 6-membered heteroaromatic group, or a 8- to 11-membered bicyclic group, any of which groups is optionally substituted by 1, 2, 3 or 4 substituents selected from the group consisting of: halogen, cyano, C1-4alkyl, haloC1-4alkyl, C1-4alkoxy and C1-4alkanoyl; R5 is isoxazolyl, —CH2—N-pyrrolyl, 1,1-dioxido-2-isothiazolidinyl, thienyl, thiazolyl, pyridyl or 2-pyrrolidinonyl, wherein each group is optionally substituted by one or two substituents selected from: halogen, cyano, C1-4alkyl, haloC1-4alkyl, C1-4alkoxy and C1-4alkanoyl; processes for their preparation, intermediates used in these processes, pharmaceutical compositions containing them and their use in therapy, as modulators of dopamine D3 receptors, e.g. to treat substance related disorders, as antipsychotic agents, premature ejaculation or cognition impairment.