envelopes

is it cynical of me to suggest that ESA 50 prepaid return envelopes are not big enough to fit any additional information, or indeed to fit A4 paper, in order to try to limit that additional information

Would it be fine to sellotape the envelope to a bigger one? Or just copy the address onto a larger envelope and then pay first class postage? The white envelope helps it stand out and will help the post openers to know an ESA50 is enclosed, I worry that a brown envelope might be somewhat overlooked. But the address on the envelope is a proper postal address (mine is the address of a former DWP office which is now an IAS / NHS building).