A compound of formula (I) wherein R1 is a C1-6 straight or branched chain alkyl group, a C2-6alkenyl group, a C2-6 alkynyl group, a C3-6cycloalkyl group or a C3-6cycloalkylC1-6alkyl group, each optionally substituted by one to three groups independently selected from: —CN; —NO2; a group —COR2 wherein R2 is hydrogen, C1-6 alkyl, —OR3 wherein R3 is hydrogen or C1-6alkyl or NR4R5 wherein R4 and R5 are independently selected from hydrogen or C1-6 alkyl; a group —S(O)mR6 wherein m is 0, 1 or 2, R6 is hydrogen, C1-6 alkyl, hydroxy or NR7R8 wherein R7 and R8 are independently hydrogen or C1-6 alkyl; a group PO(OR9)2 wherein R9 is hydrogen or C1-6 alkyl; a group NR10R11 wherein R10 and R11 are independently selected from hydrogen, C1-6 alkyl, —COR12 wherein R12 is hydrogen or C1-6 alkyl, or —S(O)m′R13 wherein m′ is 0, 1 or 2 and R13 is hydrogen or C1-6 alkyl; halo; or a group —OR14 wherein R14 is hydrogen, C1-6 alkyl optionally substituted by one to three halo atoms, C6-10 aryl or —COR15 wherein R15 is hydrogen or C1-6 alkyl; p is 2 or 3, q is 1 or 2 and n is 0 or 1 and all salts, esters, amides and physiologically acceptable prodrugs thereof; pharmaceutical uses and formulations therefor; and processes for their preparation are disclosed.