You should be able to increase your clothing allowance with regard to you having to buy a few suits for your new job, as regards a laptop and flying, surely these will be provided by your employer?
If you are genuinely incurring additional costs which are not covered by your employer, as a condition of having the pay rise, then these will need to be taken into account before any increae in your IVA payments.
I too used to work for an employer, several years ago now, who was stingy with covering work expenses. Eg: business mileage at 10p per mile, rather than HMRC's then rate of 40p per mile.
I employed an accountant, who charged me £200, to complete at tax return. The result, a £1,700 tax rebate from HMRC. I've employed an accountant every Year since (have to really, now that I am self-employed).
A decent accountant will normally charge you £200-400 per year for doing a tax return (shop around). But you may recoup that fee in tax rebates, if you have work related expenses that are not paid by your employer. (Particularly if your payrise is not itemised on your payslip as 'expenses'). Worth keeping receipts for things like buying meals whilst at work as well - you can usually claim tax relief on it all.
Good luck.
My opinions are just that: Based on my experience and being a self-employed IVA customer.
