I cannot speak for Borneo, but Malaysia is really good value, flights to KL are pretty cheap for the SEA area, and hotels, food and ubers are cheap, local transport is even cheaper, it is very safe. People are lovely. You can get a hotel with small pool in KL for about £30 per night if you shop around. KL airport is a long way out but there is a rail link (probs cheaper in an uber if there are 3, although not quicker) get an e-SIM. Food is cheap, and nice. Fake markets have teenagers in raptures. We also went to Genting Highlands (this isn't everyone's cup of tea but it is teenager paradise) again, only about £15 in an uber, maybe £40-£50 for hotel. Went up the coast on the train (again, cheap, easily bookable, stayed in Ipoh, and Taiping (not particularly recommended, but nice enough) then over to Penang (actually, one place I am not keen on, been twice, dirty and overcrowded) then flew to Langkawi (great place, good beaches, nice island). I would probably just fly from KL to Langkawi if I did it again. We stayed in a real budget place on langkawi first time (£22 a night, Casa Idaman, and it was fine enough, small pool, basic) but we stayed this time at the Bayou hotel, at around £55 and it was fabulous, brilliant pool, fab breakfast, spotless, great staff, stuff for kids etc. free snacks, 10 mins walk to main stuff, normal bar. Go to Kuah the capital when the night market is on. Such a lovely country to visit. I would not do a "tour thing", I would do it myself, half the cost, and much better opportunities with a bit of research. xx