you can get a 60 free entry stamp on arrival…leave within 60 days go to Nepal for say a week or so then return and get another 60 day stamp on arrival as it’s just been changed to 60 day stamp for uk passport holders
On the plus side of all this I hear a rumour that you may be getting 60 day visa free stamp as from Monday 14th…and extend that at immigration for a further 30 days each stamp…90-+ 90 = 180….plus x2 land crossing with 2 visa free entry stamps plus extension = 180 will be almost a year…..until someone clamps down on it
Land crossing x2 per year (1st jan to 31st dec) by air is until the immigration decides your living there on tourists visas…so it won’t be unlimited times….at a wild guess id say you’d probably get away with around 9 months stay until they stop you entering